Method and Apparatus
For Testing Call Paths over Long Distance Carrier
Networks
United States Patent
5,479,473
Zey
December 26,
1995
Method and apparatus for
testing call paths over long distance carrier networks
Abstract
A remote test site is connected to a maintenance port
of a long distance carrier switch. The remote test site
is capable of placing calls through the maintenance port
of the long distance carrier switch, testing from the
switch forward to the called party for any trouble
occurring in the elected call path. A test site terminal
connected via an X.25 network, permits remote access to
the test site. Segments of a calling path are identified
via the test site terminal to the remote test site. Calls
are placed through various long distance carrier switches
involved in a call path to isolate the trouble occurring
in a path reported by a dissatisfied customer. Calls may
be placed through selected output ports of each switch
identifying to the maintenance port of the switch the
output port number and the destination digits for the
call.
Primary Examiner: Chin; Stephen Assistant Examiner: Loomis; Paul Attorney, Agent or Firm: Pollock, Vande Sande
& Priddy
Claims
What is claimed is:
1. A remote test facility for testing a call path of a
long distance carrier comprising:
a remote test site connected by a first T1 carrier to a
maintenance port of a first switch of said long distance
carrier, for placing a call through a selected port of
said switch to a desired destination and connected by a
second T1 carrier to a maintenance port of a second long
distance carrier switch connected to said first long
distance carrier switch, permitting said call to be made
through a selected port of said second switch, whereby
first and second portions of a call path are tested to
isolate a fault in said call path; and,
a test facility terminal connected to said remote test
site for identifying to said remote test site said
selected port of said switches and a destination of a
call path to be tested.
2. The remote test facility of claim 1 wherein said test
site initiates a remote digital loop-back to a DSU of
said destination when said call has been placed.
3. The remote test facility of claim 2, wherein said test
site commands said remote test site to perform a pattern
test over said placed call and loop-back connection.
4. A method for remotely testing a call path through a
long distance carrier switch comprising:
determining a calling path from a call which has been
placed through said long distance carrier switch by
consulting a log of said switch containing call
information;
remotely placing said call through a maintenance port of
said switch through an output port identified in said
switch log over said calling path to a destination; and,
measuring the performance of said calling path.
5. The method of claim 4, wherein said method of
measuring the performance of said calling path comprises:
establishing a remote digital loop-back to a destination
DSU; and,
applying a test pattern to said calling path and
measuring a response through said digital loop-back.
6. A method for remotely testing call paths in a
telecommunications system which interconnects a plurality
of local telephone companies through a plurality of
switches interconnected by long distance carriers
comprising:
connecting a test facility to each of said switches,
permitting said test facility to place a call through a
selected port of said switches;
connecting said test facility over a data network to a
support station to permit said support station to request
said test facility to place a call through any of said
switches through a selected port of said switches to a
selected destination;
determining at said support station a call path which has
been reported by a customer as being troublesome,
including the switches through which said customer's call
was routed, and an output port of each of said switches
over which said call was placed; and,
requesting from said support station said test facility
to place said call through each of said determined
switches and determined output ports to the destination
of said customer's call isolate a troublesome portion of
said call path.
7. The method for remotely testing call paths in a
telecommunication network of claim 6, further comprising
placing each of said calls through a maintenance port of
said switches by identifying to said maintenance port an
output port and a destination to receive said call.
8. The method for remotely testing call paths in a
telecommunications network according to claim 7,
comprising:
establishing a loop-back with a local telephone network
servicing said destination after placing each call; and,
monitoring the performance of the path established by
said call over said loop-back.
9. The method according to claim 8, wherein said step of
monitoring further comprises applying a test pattern to
said test path.
10. The method of claim 6, wherein said support station
transfers said requests as a data message over an X.25
data or T1 network.
11. The method of claim 6 further comprising establishing
verbal communication to said destination over said call
path.
12. A method for remotely testing a call path established
over a telecommunication system which interconnects a
plurality of local telephones, when said call path is
reported to be substandard by a calling party using said
call path, comprising:
connecting a maintenance port at each switch of said
telecommunication network to a remote test site via a T1
carrier;
connecting each remote test site via a data network to a
central testing facility which forwards digital commands
to said remote test site;
determining from said central testing facility a first
switch of said call path which is connected to said
calling party and each remaining switch of said call
path;
issuing a command from said central testing facility to a
remote test site connected to said first switch, to place
a call through a maintenance port of said first switch
over said call path;
testing said call path from said test site connected to
said first switch;
issuing subsequent commands to a maintenance port of each
remaining switch of said call path via a connected test
site to establish a remaining portion of said call path
from said subsequent switches in said call path; and,
testing each remaining portion of said call path
established by each of said remaining switches of said
call path.
13. The method for remotely testing a call path according
to claim 12, further comprising:
establishing a call back communication circuit between
said central facility and a test site placing a call over
said call path; and,
monitoring at said central facility via said
communications circuit call progress signals generated by
placing said call over said call path.
14. The method for remotely testing a call path according
to claim 12, wherein each portion of said call path is
tested by establishing a loop back over said portion of
said call path;
transmitting a transmit pattern over said call path and
loop back; and,
monitoring the performance of said call path and loop
back to said transmit pattern.
15. The method for remotely testing a call path according
to claim 12, wherein said central facility includes in
said command for placing a call through a maintenance
port of a switch the identity of a port through which
said call is to be placed.
16. The method for remotely testing a call path according
to claim 12, wherein said command is formulated with a
dialing plan which was used by said first switch to
establish said call path for said calling party.
Description
The present invention relates to the testing of telephone
and packet-switched services over a long distance carrier
network. Specifically, a system for testing and measuring
the performance of each segment in a call path reported
to be malfunctioning is described.
Long distance telephone carrier networks which carry both
voice and digital traffic employ a variety of
interconnecting links and trunks to provide a
telecommunication path between customers. The originating
telephone or data traffic will first pass through a local
telephone company network. Telephone traffic may be
digitized, and the digitized data is sent via a T1
carrier link to a centrally-located switch. Dialing
digits originated by the customer will identify to the
connected switch the destination address of the called
party. The switch interpolates the dialing digits and
makes a connection to an outgoing port which is connected
by a dedicated link to yet another switch at a location
closer to the called party. By interconnecting various
switches, and routing the call based on the destination
digits, it is possible to make a connection with a
distant local telephone company servicing the called
party's telephone or data line. The remotely located
local telephone company will connect to the called party
the incoming call processing signals and return a ringing
signal to the calling party until the called party can
respond by going off-hook.
The connection through each of the network switches is
under control of the calling and called parties. Once the
called party has gone off-hook, and the call processing
is completed, the two parties may exchange information,
either over voice channels or through a connected data
stations.
If a calling party experiences trouble in obtaining a
path having inadequate signal-to-noise ratio, or which
suffers from other performance-limiting conditions, the
calling party may complain to the long distance carrier.
The long distance carrier investigates customer
complaints about the call path performance. Each segment
making up the call path is tested to identify the segment
causing the problem.
Complaints from a calling party are generally received in
a central location which directs efforts to test the
called circuit path. Presently, it is possible for a long
distance carrier to initiate a check of the circuit from
the first switch to receive the calling party's traffic,
backwards to the calling party. This will permit
isolation of this segment of the call path to determine
whether it may be the source of the reported trouble.
Testing from the first switch connected to the calling
party outward, to other switch locations and to the
called party's local telephone company presents a more
difficult problem. Any attempt to route a call from the
first or subsequent switches of the long distance carrier
to isolate other call path segments requires tests to be
conducted at the actual switch sites. These tests require
that appropriate switch ports involved in the call path
be identified, and a call be placed from the switch over
the identified ports. The procedure must be repeated at
each switch encountered in the call path until the
segment containing the problem is located. The process
involves personnel at each switch location in the call
path to initiate a call from each switch to the called
party.
The procedure for isolating troubles in the common
carrier network is equally applicable to both telephone
traffic and data service. In order to effectively compete
in an environment where more than one long distance
carrier is available to customers of the local telephone
networks, performance troubles must be isolated quickly
and corrective measures quickly taken.
Isolating particular segments of a long distance call
path is tedious because the call path between customers
may change each time a call is placed. Therefore, the
exact routing of a call which was reported to be of
sub-standard performance must be determined, so that the
identical path may be tested.
SUMMARY OF THE INVENTION
It is an object of this invention to provide for testing
of circuit paths used in a particular call by a long
distance carrier.
It is a more specific object of this invention to provide
for testing of each segment of a call path which has been
reported to contain a trouble from a central location.
These and other objects of the invention are provided by
an apparatus and method which will test from a central
location each segment of any call path created by a long
distance carrier network.
Each of the switches of a long distance carrier network
includes at least one input port configured as a
maintenance port. The configured maintenance port permits
calls to be placed through any specifically selected port
of the switch. This call is initiated by identifying the
called party's destination, as well as the output port
over which the call is to be placed. Thus, it is possible
to test through the same switch output port and its
connected link which was involved in a call path reported
as having a trouble.
The invention advantageously provides for the remote
placement of calls from a central location through the
maintenance port of each switch. Each of the output
switch ports involved in a call path can be individually
selected and a call placed to the same party which was
the subject of the customer's earlier call which
generated the complaint. In this way, it is possible to
test each call path segment by segment, from the
originating switch through all intermediate switches to
the final destination local area telephone company.
In carrying out the invention, a digital remote test unit
is located at a central location and includes a T1
carrier interface which connects to each switch with the
DS.phi.S configured as maintenance ports of the long
distance carriers switches. More than one remote test
unit may be utilized to divide the network switches into
a manageable group to be accessed by the individual
remote test units.
Whether one or multiple remote test units are employed,
they are network connected to a single test site. The
single test site comprises a computer terminal which can
communicate over the network, receiving as well as
transmitting commands to each of the remote test sites
employing a remote test unit.
In accordance with the preferred embodiment of the
invention, the test site, through conventional means,
will determine the network call path which resulted in a
trouble report being filed. By making inquiry to each of
the switches, it is possible to identify from the log
contained in each switch the particular input and output
port over which the trouble call was placed. Having this
knowledge, it is possible to command a remote test unit
to place the call through the maintenance port of each
switch involved in the connection. The maintenance port
will place the call through the identified output port
and link connecting the output port to the next switch in
the call path which resulted in the customer's complaint.
Alternatively, the maintenance port can place a call
through an input port, servicing the trouble call back to
the customer.
Each switch is tested so that the output port and link
connecting the output port to the next switch involved in
the call path is isolated from the previous portion of
the connection. As the call is placed over each of the
switches through the maintenance port, it becomes
possible to identify a segment connecting the switches
which is the source of the reported trouble.
The invention also permits the call path from the first
switch backward to the calling party to be tested. By
accessing a DAX connected to the local telephone company
network, it is possible for the remote test unit to place
the call in this direction.
The invention permits testing in both voice circuits, as
well as data circuits, such as switched 56 services which
utilize the common carrier network.
The testing system, in accordance with the present
invention, permits various standard tests to be made from
the test site. These tests include establishing loop
back, or termination conditions between the output port
which was seized by the maintenance port on command, and
the destination party's equipment or dialing into the
local telephone company switch test numbers. Accessing
and initiating the loop-backed call, or test number,
permits test tone measurements, data pattern responses
and noise measurements to be made.
DESCRIPTION OF THE FIGURES
FIG. 1 illustrates a common carrier network employing a
testing system in accordance with one embodiment of the
present invention.
FIG. 2 is a flow chart illustrating a test scenario
conducted from the test site for voice frequency
channels.
FIG. 3 is another test scenario conducted from the test
site of voice channels using quiet term, test tone or
loop back features.
FIGS. 4A and 4B show a testing scheme in accordance with
one embodiment of the invention for testing switched 56
circuits of the common carrier network.
FIG. 5 shows in another embodiment of the invention for
testings switched 56 data circuits.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown a common carrier
network which interconnects local telephone company
networks 6 and 17. Traffic can originate from either of
the local area telephone networks (TELCO) 6 or 17, and be
connected to the other TELCO via a plurality of digital
switches 11, 12 and 13. The digital switches 11, 12 and
13, as will be apparent from FIG. 2, have a plurality of
input and output ports. The input ports connect either to
a local telephone network 6 or 17, or in some cases to a
leased line, permitting direct customer access to one of
the common carrier switches 11, 12 and 13.
The channel banks 14 and 16 provide a plurality of
DS.phi.S which are embedded within the T1 link which
directly connect the switches 11, 12 and 13. The input
channels represented by DS1 comprise up to 24 T1 DS.phi.
channels which a corresponding switch 11, 12 or 13 will
connect a DS.phi. to an output port of the switch. The
output ports of the switch are directly linked to a
second switch at a different geographical location over a
dedicated link which terminates at an input port of a
distant switch.
When a call is placed by either the voice station 22, or
data station 21, the appropriate channel card for voice
or OCU for SW56 (16) provides the call process signalling
to the station 19 or 22 which has gone off-hook. The
off-hook station transmits the destination digits of the
called party to which a communication path is to be
established.
The TELCO 17 conveys to the respective connected switch
13 the destination digits for creating a path to the
called party which may be telephone station 15 or data
station 9 or 10.
The channel bank 16 creates 24 DS.phi. channels which are
connected to the switch 13 at DS.1 level. The switch 13
will decode the called party's calling number and select
an output port based on various routing criteria
established in the industry for signalling an adjacent
switch, i.e., 12 or 13, to make a call path connection
with switch 11.
The switches 11, 12, 13, engage in a protocol of their
own to set up the call with the TELCO 6 identified by the
calling digits. The TELCO 6 will provide a ringing signal
to either the called voice station 15 or called DSU 7 for
data station 9, depending on the decoded calling digits
it receives.
The foregoing process of establishing a call path is
utilized in most modern common carrier networks. Once the
call path is established it is possible that one or more
of the segments of the call path may introduce noise,
attenuation or some other performance limiting anomaly
interfering with the quality of the call path. A
customer, operating either voice station 22 or data
station 21, will initiate a trouble report which is
called in to a test site 33. In accordance with the prior
art, an operator at the test site 33 has the capability
of connecting to a test system 26. The test system 26 and
test site 33 are linked over an X.25 data packet network
through a site controller 30 and a primary node 32 of the
X.25 data network. The test system shown in 26 may be a
Hekimian model 6700 remote testing device. The testing
device 26 includes a T1 carrier interface, and T1 link 24
connecting the test device 26 to the T1 interface 11a of
switch 11. A second T1 carrier 25 connects the test
system 26 to the T1 interface 12a of switch 12. The
DS.phi.S within this T1 11a would be configured as
maintenance ports within switch 11.
Also shown is a second test site, including a test system
29 connected via a respective site controller 31 in the
X.25 data network. Using the of test devices 26, 29, it
is possible to initiate test procedures with each of the
switches from test site 33.
A DAX 23 is shown, which may also be connected via a T1
carrier link 20 with the test device 26. The DAX 23, as
is common in network architecture, connects to a TELCO or
customer having a dedicated T1 carrier 27. The DAX 23 is
also connected via a T1 carrier link 28 to the switch 12.
T1 carrier link 27 will include 24 DSOs, i.e., channels
which are terminated via a T1 interface on switch 12 to
24 ports of the switch. One of the ports and DSOs serving
the port can be configured as a maintenance port,
permitting the test system 26 access via the DAX 23 to a
port configured as a maintenance port on switch 12. In
this way, the test system has the capability of accessing
a maintenance port on the switch through the DAX or
accessing a connected customer or TELCO through the DAX,
permitting checking all path segments towards the
originating caller as well as away from the originating
caller in the direction of the called party.
Through either the DAX 23 or directly to a port
configured as a maintenance port, such as 11a of switch
11, the test system 26, via the maintenance port, can
access any other port on the switch, both input and
output ports in the call path being checked. In the case
of an input port, it may be useful to access an input
port which was used in a call path being tested by
seizing the input port and testing the circuit from the
input port back to the originating caller. This scenario
may be accomplished through a DAX as well by using one of
the channels of the T1 link connecting the DAX 23 to
switch 12 to access a port configured as a maintenance
port. The maintenance port can thereafter be used to
place a call either to a port which serves as an input
port to a call which resulted in the trouble report, or
through the switch exiting the output port involved in
the call.
Before discussing the operation of the test devices 26,
29 in connection with the site 33, the description of the
architecture of each of the switches 11 through 13 will
be made.
Turning now to FIG. 2, there is shown an architectural
drawing of the cross-connect switches 11 through 13. Each
of the switches 11, 12 or 13 includes trunk groups with
connections at DS.phi. level. Each DS.phi. level
connection is called a port. The manufacturers of the
digital switches provide for configuring any one of the
ports as a maintenance port. In this example, the
maintenance port was configured from the 24th DS.phi. of
the T1 interfacing the switch. The remaining 23 DS.phi. s
were configured as ports within trunk group 78.
FIG. 2 illustrates a DXC 1/0 interface 24 connected to
the maintenance port of the switch 11. The DX 1/0 switch
permits connection to the test system 26 which, as was
noted, may be the Hekimian Model 6700 test device. The
DXC 1/0 permits the 6700 to place a call through any
selected output port of the switch when a DS.phi. from
the DXC port 35 to the switch is configured as a
maintenance port, as well as permits connection to be
made via a second port 34 to a local TELCO. The DXC 1/0
permits calls to be routed either through the switch 11,
or back towards a calling party through port 34, thus
checking all segments of a call path.
With an appropriately configured maintenance port on the
switch 11, it is possible to dial the port number from
the test system 6700, followed by the called party
destination number of a reported call trouble. In this
way, any output port of the switch 11 can be selected,
permitting the connection from the output port to the
next switch to be tested.
The remaining ports of FIG. 2 are illustrated to show how
various customers and local TELCOs interface with the
switch. The output ports are all connected to other
switches identified as PDL HSN NOR WAE and AST, which are
geographically located to serve other TELCOs and
customers via dedicated lines.
The switch 11 includes a log which identifies each call
which has been placed through the switch by originating
number, destination number and output port over which the
call was placed. In carrying out testing of a call path,
this information is retrieved from the switch via a
terminal at the test site 33, which is connected via a
telephone network to the local switch, which originated
the call over the troubled calling path.
Returning again to FIG. 1, it is clear that the test site
33, based on the calling number obtained from the
customer or through ANI, can identify which switch was
initially involved in establishing the call path. An
inquiry can be made from the test site 33 over a
conventional telephone link to the switch site,
requesting the port number which was used in the switch
to connect the call to the next subsequent switch of the
path.
As each of the output ports of switches 11, 12 and 13 are
dedicated output paths to a subsequent switch, a test
call can be placed to the originating switch placing the
test call through the same output port of the circuit
path which was identified as having a trouble.
It will be evident with respect to the flow charts of
FIGS. 3, 4 and 5, that the test site 33 can command the
test system 26 via the X.25 data network to place the
same call as resulted in the trouble to the maintenance
port of the first switch involved. Thus, in the case of
voice station 22, or data station 21, that had originated
a call to station 15 or 9, which resulted in a trouble,
the test system 29 would initiate, via the maintenance
port of digital switch 13, the same call to the same
destination 9 or 15. The call so completed through the
maintenance port will permit an evaluation at test site
33 of the call path performance, using the various known
measurement techniques.
In the event that a trouble is identified as being on the
call path, it can be assumed that it exists somewhere
between the digital switch 13 and the called party 15 or
9.
Where a DAX is employed at the switch, it is also
possible for the test system 29 to place a call back
through to the calling party 21 or 22 and verify that
portion of the path is performing appropriately.
In the event that the test call placed from switch 13
outwardly to the called party 9 or 15 identifies a
trouble within the call path segment extending from
switch 13, the subsequent test call can be placed from
the next adjacent switch in the call path. As each output
port is connected by a dedicated link to the next switch,
it is easy for the test site 33 to identify the second
switch in the path segment handling the call.
In the event it is determined that switch 12 is the
second switch, it is possible to command the test system
26 to place the same call through the maintenance port of
switch 12, via the T1 carrier link 25. Once again, an
inquiry is made to the switch 12 to determine the output
port of switch 12 which handled the original call which
was subject to the trouble. The log of switch 12 will
yield the output port of switch 12 which carried the
original call, as well as the follow-up test call.
The test system 26 then places the same call to the same
destination over the maintenance port of switch 12 via
the T1 carrier link 25.
The process is repeated until the final switch within the
call path has been identified. At this point, the trouble
can be isolated to the local TELCO 6, and corrective
action taken from that point by the local TELCO
representatives.
Each of the TELCOs includes DSU 7, 8, 18 and 19 which
provide for the signalling between its customers and the
TELCO central office. As is known in the telephone
communications art, it is possible to conduct various
tests between the DSU, customer TELCO switch and a call
site. These would include a loop-back arrangement
permitting calls originating from test site 33 to monitor
the result of various test patterns which are sent down
to the DSU and returned via the call path, as well as to
monitor quiescent noise levels and to send and/or measure
various tones to a respective TELCO switch test numbers
involved, as well as verbal communication with the
customer over the same circuit. The present invention
will permit these types of tests to be made from each of
the switches involved in a call path which has generated
a trouble report.
Turning now to FIG. 3, there is shown a first scenario
for conducting tests of voice circuits which have been
reported to have a trouble. The steps depicted in FIG. 3
illustrate the sequence of operation between the test
site 33 and the test system 26 or 29.
The remote tester at test site 33 comprises a computer
terminal which will generate menus for the operator to
select a test to be conducted. The prompt 42 directs the
operator at test site 33 to select the type of switch,
i.e., DEX switch/VF, to be accessed by the testing system
26.
The remote tester at test site 33 would select either
voice frequency VF or SW56 from the menu 42, depending on
whether voice service or switched 56 service (a data
service) is to be tested.
Finally, a prompt 43 is given to the test site terminal
to select the port through which a call is to be placed
and a dial plan. By executing a command such as CO IRV
TAD, the test system 26 is commanded to select the first
available DS.phi. T1 channel over the T1 24 for direct
access to the maintenance port of the selected switch. At
this point, the circuit is still in an on-hook condition.
Assuming, for the example of FIG. 3, that the voice
service VF is selected, the operator at the test site
communicates with the appropriate data switch over a
standard communication link (not shown in FIG. 1), call
routing information is obtained from the switch which
received the call which resulted in the trouble report.
By interrogating the call routing table of the switch, it
is possible to determine an entry corresponding to the
calling party's ID, the destination party's ID, and a
port number of the switch which was involved in the
trouble. With this routing information, the test site
operator can enter the following dial plan in step 43 in
response to a prompt issued from the test system 26 the
test site terminal 33. The dialing plan would be as
follows:
DIAL 34264538# DTMF 703 842 4587
34264538 corresponding to the outgoing port of switch 13,
which is connected to switch 12. Alternatively, the user
can enter a path corresponding to a circuit from the
switch 13 back to the customer placing the call. This
dial plan would be as follows:
DIAL 29475447# DTMF 734 9534.
When the test site operator hits the return key on
terminal 33, the inputted commands are transferred over
the X.25 network to the remote Hekimian test system 29.
The test system, via the T1 carrier link 27, will seize a
channel to present an off-hook condition to the
maintenance port 13a of switch 13 in step 44. This
scenario presumes that switch 13 was the first switch in
the long distance carrier network to receive the call
originated from the calling party 22.
The maintenance port 13a of switch 13 will decode the
foregoing dial plan and seize the outgoing port 34264538
identified in the dialing plan. The switch 13 output port
identified in the dialing plan will seize a line
connected to the next switch in the call path, assumed to
be switch 12. Once the dial tone is returned back to the
test system 26 from switch 13 in step 45, the port number
for the selected path is sent to switch 13 and upon
seizing the outgoing port to switch 12 in step 47, the
dial plan and destination number are transmitted in step
46 to switch 12.
Once the port number is received by switch 13 the
incoming port of switch 12 is seized in step 47. The
destination number is then dialed over the output port to
switch 12. The information received at the subsequent
switch 12 is translated and the call placed to the
subsequent switch 11. Once again, the received dialing
plan in the input port to switch 11 is routed in step 48
to the appropriate TELCO 6 via a channel bank of one of
the 24 DS.phi.s on the T1 carrier link.
Thus, the routing path for the original call has been
repeated for the call placed through the maintenance port
of the originating switch 13. Once the destination TELCO
6 switch has received its ringing voltage, and answers by
going off-hook in step 49, this condition will be
monitored by the appropriate test system 26. A command
sent over the X.25 network notifies the test site
terminal 33 that the call has been placed. At this time,
the test site operator can select from further prompts in
step 50 on the test site terminal 33 the type of test to
be conducted over the call path selected. These can be
either quiet termination, test tone, or a loop-back
condition. The menu presented at the test terminal 33
will also permit various noise tests and tone level
measurements to be made. A loop-back condition can be
selected from the test terminal site 33 for conducting
conventional loop-back tests.
Once testing is completed, the connection is broken by
having the test terminal site issue a HANG command in
step 51. This will command the test system 26 or 29,
depending which has initiated the call, to break the
connection by going on-hook again in step 52.
The foregoing process can be repeated for each switch in
the call path. Assuming that a trouble was detected on
the tested call path, the process of FIG. 3 may begin
again by selecting a dial plan which is initiated through
the second switch 12. If the subsequent testing in
accordance with FIG. 3, through the maintenance port of
switch 12 does not clear the trouble, it can be assumed
that the trouble lies between switch 12 and the
destination station 15. The dialing plan is obtained by
doing another search within the connection table of
switch 12 for the output port involved in the tested
circuit path. Once the output port is obtained, another
dial plan is entered, using the same destination number
and output port number. The series of tests shown in
block 50 are again repeated. In the event the trouble
exists in the dedicated link between switches 12 and 13,
this condition will be identified, and corrective
measures may be taken.
The foregoing is a simple test scenario which can be
carried out using the system of FIG. 1. A more involved
testing routine is shown in FIGS. 4A and 4B for testing
voice circuits which have been reported to have a
trouble. The test scenario begins from prompts which are
available at the test site monitor 33, originated from
the test system 26 or 29. The prompt will request
selection of the switch type, i.e., DX or DEX switch, and
service type, i.e., VF for voice service. The prompt 60
will also permit a request for a call-back number,
permitting the test system 26 to call a test site
operator over a voice channel. The call-back number is
entered as part of the command in response to a prompt.
When this command is received by the test system 26, an
available phone line is seized by the test system 26, and
the call-back number is entered in step 61 placing a call
to the test site. Once the test site goes off-hook
answering the call in step 62, the call can be placed in
a monitor state in step 63, permitting the call progress
of calls made from the test system 26 through the
maintenance port of a selected switch to be monitored.
Placing the call through a speaker phone in step 64
permits the test site to monitor the call progress over
the dial plan that is entered in the subsequent prompt.
Further, a verbal communication can be established
between the remote test site 33 and the called party.
The next prompt 65 requests a dial plan to be entered, as
was done in FIG. 3. A port number, established from doing
a table search of the first switch in the call path
reported as having a trouble is entered. The string
command, representing port number, dial plan and
destination number, would appear as follows:
DIAL 284617483# MF*706 34576453#.
This command represents multi-frequency signalling
placing a call to the destination corresponding to the
destination of the reported trouble.
A similar path may be selected from the switch back to
the originating calling party. Such a command would
appear as follows:
DIAL 25091735# MF*7651294#.
Once the dial plan has been entered in 65, and the return
command given at the site terminal, the test system 26
will attempt to connect the selected switch 13. Protocol
involved in step 66 requires a start loop signalling
mode, a time period to wait for the seizure, followed by
a dial tone. When this portion of the protocol is
completed, the test system 26 will initiate the dial plan
digits including port number, destination number to the
maintenance port of the selected switch in step 67.
The switch in step 68 will seize the port identified from
the command, and in step 69 connect the seized port of
the switch 13 to the maintenance port.
The switch 13 will seize the input port of the next
switch 11 in the call path in step 70.
Step 71 represents the routing of the call by the
remaining switches in the call path to the customer based
on the dial plan.
The called party or the connected TELCO switch answers in
step 72. The off-hook condition is forwarded to the test
site monitor 33 in step 73, identifying to the test site
terminal 33 that the call has been placed.
All during the foregoing, the test site operator, by
listening to the speaker phone, has been able to monitor
the call progress, giving the test site operator some
insight into whether the call placement has experienced
any difficulty.
Once the destination party 15 has gone off-hook, the
tester's call back circuit is placed in the split mode in
step 74. This will permit the test site operator to
communicate verbally with the called party through the
established call path.
The tests referred to in FIG. 3, i.e., test tones, quiet
terms, and loop-backs, can be effected by generating the
appropriate commands from the test system for appropriate
testing to the TELCO test number dialed. These tests are
standard industry tests which may be carried out without
further description.
The foregoing system for testing call paths is adaptable
in data communications as well. In the switch 56 service,
customers take advantage of the dial up access of MCI
switches, and pay only for the time a circuit is in use,
saving any monthly access charge that may be applicable
to other services. FIG. 5 illustrates the steps carried
out by the same hardware used to test the switched 56
data circuits of the long distance carrier.
Referring now to FIG. 5, the process begins from a series
of prompts 80, which appear at the test site terminal 33.
The user selects whether the test is over a switch 56
circuit or a voice circuit. The switch type is selected
as either DMS switch or DEX switch, as is known to the
test site operator. As in the VF service, a test is
conducted when a customer reports a trouble in a call
path originated by the customer from a data terminal 21
to a second terminal 10 via the long distance carrier
network.
The dial plan is entered in step 81 at the remote tester
terminal, and assuming that a test of the outgoing port
of the originating switch is desired, the dial plan would
be as was in the previous tests, i.e.,
DIAL 34264538# DTMF 703 842 4587.
The incoming and outgoing ports are determined from doing
a call search in step 82 as was done in the previous
example via a connection to the particular switch which
originates the data traffic, which, in the illustration
of FIG. 1, is switch 13. Having established what the
outgoing port is, the dial plan is entered in step 83 by
identifying the port number, dial plan and destination
number. The entered data is forwarded via the X.25 data
or T1 network to the test system 29. The test system 29
will go off-hook in step 85 and when it detects a tone
returned in step 86 from the maintenance port 13a of
switch 13-3, it will begin to transmit to the maintenance
port the calling data in step 87.
The maintenance port 13a, upon receiving the dial digits,
will select the output port identified in the dial plan
to begin the call placement to the next switch 12 in the
series. Switch 12 will translate the destination number
into a routing plan in step 89 and eventually the call
will be sent over the network to the destination DSU, via
a private line configuration or through a TELCO access
tandem switch in the event of feature Group D switched 56
service, as represented in step 90, the destination DSU
being identified as 8 in FIG. 1 for the data station 10.
When the data station 10 goes off-hook, the condition is
reported from the test system 26 to the test site 33 via
a prompt 91. At this point, the remote test site 33 may
engage in standard testing of the circuit established. An
RDL loop-back may be requested in step 92 at the test
site 33 remote tester. Various known transmit patterns
are transmitted in step 93 over the circuit path
established, and back from the RDL loop-back. Performance
may be measured for this standard test, and as was done
in voice frequency, subsequent calls placed over
subsequent switches in the call path to isolate a problem
segment of the call path.
At the conclusion of any such tests, the test site 33 may
command, in step 94, to release the RDL loop-back. Upon
receipt of an appropriate prompt in step 95, the test
site 33 remote tester may issue the HANG command 96,
ending the test session. As in voice frequency, the test
systems 26 and 29 respond to the HANG command by
releasing the calls to the particular connected
maintenance port, resulting in a tear-down of the call.
Thus, there has been described a system which will permit
remote testing of all circuit paths which appear to be in
trouble. This remote testing will isolate a segment of a
call path without requiring personnel to be present at
each switch location, expediting the clearing of
troubles. Those skilled in the art will recognize yet
other embodiments of the invention defined by the claims
which follow.
![[US Patent & Trademark Office, Patent Full Text and Image Database]](Patent%205,479,473_files/patfthdr.gif){kind=small}
