JPH0342744B2 - - Google Patents

Description

Claim 1: A method for identifying failures of interoffice trunk circuits arranged as a group in a communication system, comprising: a threshold for the number of unanswered calls of an interoffice connection via each trunk group during a first time interval; is configured for testing purposes, counts the number of unanswered calls for each trunk group during a first time interval, compares the actual number of unanswered calls with the configured threshold, and determines whether there are more unanswered calls than the threshold. The number of unanswered calls for each trunk circuit in the group indicated by the number of calls is
and recording an identification number of each trunk circuit that exhibited a number of unanswered calls greater than a threshold during a second time interval. Method.

TECHNICAL FIELD The present invention relates to a method for identifying faulty communication lines in a communication network, and more particularly to a method for identifying faulty communication lines between nodes in a communication network.

BACKGROUND OF THE INVENTION In recent years, there has been increasing interest in automating the detection of failures in communication networks. Much of the interest concerns the common circuitry at each node used by all communications through the node.
Failure analysis of the large number of functional circuits used to interconnect the nodes of a network is generally considered to be less important than common circuits and is less developed. Unlike most common circuits, these circuits cannot often be continuously monitored in an efficient and cost-effective manner.

In communication systems, the functional circuits that interconnect the nodes of a network are called trunks.
At different times it is a shared facility used by different customers of the network. Trunks interconnecting any two nodes are typically grouped into trunk groups of various sizes.
When setting up communications between customers associated with different nodes of the network, available trunks from the group interconnecting these nodes are selected for connection.

In some cases, critical conditions, such as loud noises, occur on the trunk that cannot be detected by routine operational testing, but are detectable by the customer. When such a trunk is used for a call, the customer using the connection will detect an unacceptable condition and will briefly terminate the call and attempt to set up the call again. Such trunks are only used briefly for each connection attempt, have very short hold times, and are repeatedly available for customer use, causing an unusually high number of incomplete calls. be. In telephone systems, these are called "killer trunks." This is because each such trunk causes an unusually high number of incomplete calls.

For example, in private networks dedicated to one large customer, such as a company or government office, the need to quickly locate failed trunks is particularly high. Such networks typically have a relatively small number of heavily loaded trunks in a group. These deficiencies often result in individuals using such networks using the same failed trunk multiple times before successfully connecting.
When a customer complains about a poor connection, it is often difficult to link the complaint to the specific trunk or group of trunks that caused the complaint.

Generally, all or many of the trunks in a group share some common circuitry. All of the group's trunks have nodes connected in common. If there is a failure in such a common circuit or connected node, multiple calls distributed over multiple trunks will not be successful. Distinguishing these types of fault conditions from failures of individual circuits in a single trunk is very important given that the methods of repair are different.

Off-line devices are commercially available that record the number of times a given trunk is seized (trials) and the percentage of time a given trunk is used (utilization or occupancy). These records can tell you which trunks have unusually short hold times (ratio of usage to number of attempts).
This would indicate a failed trunk. However, because each monitored trunk requires special equipment, these prior art systems are typically capable of making measurements on only a small number of trunks. The cost of monitoring all trunks with such equipment is very high. There is no good overall mechanism to identify which trunks or trunk groups to measure. Measuring the performance of all trunks connected to a node using such a dedicated system requires several busy times, since meaningful measurements require several busy times. This could take weeks or months.

Furthermore, such prior art systems can only be used with trunks that have direct circuit access to each trunk, whereas trunks for multiplex communications, such as digital trunks or analog carrying trunks, cannot provide such access to these trunks. You cannot use it unless you are able to do so.

SUMMARY OF THE INVENTION In accordance with the present invention, a program controlled system having groups of functional circuits used for controlling nodes of a network and communicating between nodes of such a network is provided. Detect missed communications. The number of unacknowledged communications of each group of functional circuits is measured. Groups for which the amount of unacknowledged communications is substantially greater than the amount for similarly sized groups are considered to be groups that include functional circuitry that is repeatedly used for incomplete inter-node communications. In one embodiment, this number is measured for a given time unit and represents the incidence of such unacknowledged communications for such time unit.

In one embodiment, such a number may be accumulated in a counter in a memory device associated with each such group of functional circuits. Advantageously, such numbers can be displayed on the system's maintenance console and will indicate the groups of functional circuits that have been used repeatedly for incomplete calls.

Advantageously, once a group is identified as being repeatedly used for unacknowledged communications, the usage of that group is further monitored as the number of trials per unit time for each functional circuit in the group. Ru. A functional circuit having a higher number of trials than other members in the group is considered to be a functional circuit with a high possibility of failure. Once the problematic circuit has been thus identified, routine repairs can be made.

Further, according to the present invention, a threshold value can be set for each group of functional circuits. If a group has unasserted connections exceeding this threshold during a unit of time, this group will also automatically undergo traffic measurements for its individual functional circuits.

Further, in accordance with the present invention, three types of traffic measurements are made for individual functional circuits within a group: total attempts, number of unsuccessful communications, and occupancy. These times and occupancy rates are performed for a unit time for all functional circuits within the group. The total number of trials for any one functional circuit is inherently higher than others in the group, or the number of unacknowledged communications for any one functional circuit is inherently higher than others in the group. or when the occupancy of any one functional circuit is essentially lower than the occupancy of other functional circuits in the group with a similar number of trials, then that functional circuit is considered to be faulty. be identified. According to another advantage of the invention, if measurements on individual functional circuits show relatively uniformly poor results, it is likely that a device common to the group is failing.

An example of the type of program control system to which the present invention can be applied is a communication system. A network of such systems is a communications network. The inter-node communication circuit is a trunk. In one example scheme, unsuccessful attempts and total attempts are counted for each group of outgoing trunks of the communications network. If the number of unsuccessful attempts exceeds a predetermined threshold for the group, individual trunk measurements are taken for the trunks in the group. The number of attempts to use each trunk in a group may be combined with an optional measure of occupancy and unacknowledged communications for each trunk in such group. Trunks that have a high attempt rate, a high rate of unacknowledged communications, or a low utilization rate compared to other trunks with a similar number of attempts are identified as failed. Furthermore, if the measurements of the trunks in the group show relatively uniformly poor results, it is likely that there is a failure in the common equipment of the group. If a subgroup of trunks associated with a particular device shared by a subgroup exhibits uniformly poor results, it is likely that there is a failure in that particular device. If measurements on a group of trunks from many different nodes to a node result in a high percentage of attempts that are not all positive, then there may be a failure at that node.

The rate of unacknowledged calls is a sensitive indicator of failures in the internodal equipment of a communications network. The present invention takes advantage of this property to identify specific problems.

[Brief explanation of drawings]

The present invention will be fully understood from the following description with reference to the drawings.

Figure 1 is a block diagram showing the main parts of a typical switching equipment used in a communications network; Figure 2 is a diagram of a communications network with several nodes; Figure 3 is a typical electronic telephone exchange A well-known program structure for processing telephone calls in a device; FIG. 4 shows a memory arrangement for accumulating the number of attempts, unanswered calls and usage for each trunk in a trunk group; FIG. Figure 6 shows the memory layout of the counters used to accumulate the number of attempts and unanswered calls data; Figure 6 shows the memory layout of the data identifying the trunk groups being monitored; Figure 7 shows the memory layout of the counters used to accumulate the number of unanswered calls. Figure 8 is a flowchart of a program for accumulating the number of attempts for each trunk in a trunk group; Figure 9 is a flowchart for measuring the trunk utilization of a trunk group. Figure 10 is a trunk group memory unit for identifying all trunks in the group; Figure 11 is a flowchart of the program used to identify all trunks in the group; Figure 12 is a flowchart of a program for configuring traffic data for printing; Figure 12 is a flowchart of a program that identifies trunk groups whose individual trunks are to be monitored; Figure 13 is a command to monitor a particular group. This is a flowchart of a program that responds to the following.

DETAILED DESCRIPTION FIG. 1 is a high level block diagram of such a telephone switching system. This represents one switching device or node 106 in the telephone network. The system includes a processor 100 and input/output devices 103, 104 and 105 under program control.
Contains.

Trunk and service circuits 103 include trunk circuits associated with trunks 115 connected to other switching equipment. The service circuit includes a transmitting circuit for transmitting the called number to another switching equipment and a dial receiving circuit for receiving dialing information from the customer. Customer line 114 is used to connect between customer line 114 and trunk and service circuit 103 served by this switching equipment.
A switched network is used between the trunk and the service circuit 103. A connection to the trunk circuit 103 set to the appropriate state creates a connection to the associated trunk 115.
Trunk and service circuits 103, switching network 104 and connected customer lines 114, and maintenance console 105 are controlled by processor 100 via bus 116.

When the customer picks up the telephone, the line is connected by switching network 104 to a dial receiver in 103. The processor receives data through the dial receiver indicating the request dialed by the customer. If this request is interpreted as requesting a connection to a customer served by other switching equipment, the processor selects the trunk circuit associated with the trunk connected to the other switching equipment. . Next, the superstition circuit in 103 is selected by the processor to switch to the switching network 1.
It is connected to the trunk circuit selected by 04. Once the called number has been transmitted by the transmitting circuit, the calling customer is connected to the selected trunk circuit by the switching network. The other switching equipment then makes the appropriate connection in its own switching network so that the calling customer can communicate with the called customer when the customer takes the telephone off-hook. All exchange network connections, trunk circuits, and service circuit state changes are processed by the processor 10.
0 control.

Switching network 104, trunk circuits, and service circuits, including dial receiver and transmit circuits, are well known to those skilled in the art.

Maintenance console 105 is used for communication with personnel who maintain and control the switching system. Information about traffic and failure conditions is displayed or logged on the maintenance console, from which commands can be entered. Maintenance consoles are well known to those skilled in the art.

In program control, the processor 100 is used to control the exchange equipment. Any of a number of well-known processors can be used to perform this function. Such a processor consists of a central processing unit and memory 102. Memory 102 stores groups of programs containing groups of instructions that can be directly interpreted by central processing unit 101. The central processing unit 101 executes such a program by executing the following functions in response to instructions read from the memory 102. Send control and output signals to receive input data from input/output devices. Data read from memory 102 is stored in an internal register. memory 10
Add the contents of position 2 to the contents of the internal register. The contents of the memory 102 location are compared with the contents of internal register storage. Control is transferred to an alternative program according to such results or the state of internal registers. Transfer control unconditionally to an alternative program. The central processing unit 101 also has a clock 11.
Contains 3. The clock provides basic timing. This basic timing is memory 102
Under the control of an execution control program stored in the memory 102, it can be used to derive any time span in relation to the data stored in the memory 102.

FIG. 2 shows a portion of a telephone network in which node 106 shown in FIG. 1 is one node and nodes 107, 108 and 109 are other nodes essentially similar to node 106. It is. These nodes are partially interconnected, with each node connected to at least one other node. Interoffice trunks used as communication facilities between nodes are grouped into trunk groups, all members of which interconnect the two nodes. For example, all members of trunk group 100 have nodes 106 and 1
07, all members of trunk group 111 interconnect nodes 105 and 103, and all members of trunk group 112 interconnect nodes 106 and 109. Each node has a number of trunk groups connecting it with other nodes.

It is common in telephone systems to limit the traffic of a given trunk group to one direction. For example, traffic originating from a customer served by node 106 and connected to a customer served by node 107 is routed through a trunk group such as 110, which carries only traffic originating from node 106. A corresponding incoming trunk group (not shown) will carry traffic in the reverse direction. The normal practice in telephone switching systems is that the switching equipment connected to the outgoing end of a trunk is responsible for the maintenance of that trunk, and the incoming trunk is then responsible for the switching equipment connected to the other end of the trunk. It is now being maintained.

Programs that can be executed by processor 100 to control a switching system to perform all functions necessary to handle telephone calls are well known to those skilled in the art. Figure 3 shows programs related to outgoing calls (calls from a customer line handled by that switching equipment to a customer line handled by a different switching equipment), a program for traffic measurement, and a maintenance console. It shows a program for communication. In this explanation, incoming calls (calls from customer lines handled by different switching equipment to customer lines handled by this switching equipment) are maintained by the other switching equipment, so incoming calls are No need to explain. Intra-office calls that do not use trunks are not considered.

The principles of the invention described herein are also applicable to the case of bidirectional trunks.
However, for convenience, the explanation will be given only for the case of unidirectional trunks.

The switching system operates under the control of a prior art program shown schematically in FIG. Central processing unit 10
1 executes this program to set up or restore telephone connections or perform other functions necessary for the operation of the telephone exchange equipment. The central processing unit 101 has input/output programs 210, 21
1, 213, 214, and 216 to communicate with the input/output devices 103, 104, and 105. When accumulating and processing the data necessary to detect the specific details of a customer's dialed request, the central processing unit
01, 202, 203, 204, 205 and 2
It operates under the control of 06. In the process of executing the call control program and the maintenance console message program, the input/output devices 103, 104, 105
The central processing unit frequently performs service routines 220, 220,
221, 222 and 223 are executed. Each of the programs and routines shown in FIG. 3 is comprised of a number of subprograms or subroutines for controlling particular subtasks. The central processing unit 101 may execute a jump instruction, either unconditionally, according to the result of a comparison, or by detecting a particular state of an internal register within the unit and executing a jump instruction. Request execution of a subprogram. It will be appreciated that the detection, control, and other operations of the program described herein are performed by the processing unit under the control of the program.

The system under control of the program outlined in FIG. 3 operates as follows. An outgoing call is initiated when the switching equipment detects that the customer is off-hook. This detection is performed under the control of a supervisory line scanning program 210 which periodically monitors the circuits of the switching network 104 connected to the customer lines. When the processor detects a service request, it sends the dialing connection program 20 to control the network 104 to establish a connection between the calling subscriber and the dialing receiving circuit.
Call 1. By executing the program 201, the central processing unit also selects the translation program 221, which is used to select the dial receivers available at the time, and select the route through the exchange network between the calling customer and the dial receiver. network control program 22 used to
2 and the circuit control program 223 used to set the data necessary to control the state of the dial receiver.

When the customer dials, the dialed number is collected under control of the dial pulse scanning program 211. Once the digits are collected, details of the customer's request and completion of the dialing are detected under the control of the digit analysis program 202. When this stage of the call is reached, a translation program 221 is executed which selects the trunk group of switch equipment specified by the first three digits of the dialed number and selects the trunk group in that group. The available outgoing trunk is selected. Under the control of network control program 222, network 104 is connected between a transmitting circuit in 103 operative to transmit the called customer's number to a remote switching system and the previously selected outgoing trunk. A route passing through is set. The outgoing trunk and transmitter are set to the correct initial state under the control of circuit control program 223. The data controlling the transmission of the called number to the destination exchange equipment is set under the control of the pulse transmission program 206, and then the actual transmission of the digits is performed by the transmission circuit 103 under the control of the number transmission program 214. It will be done.
Once the process of sending the called number to the destination switching equipment is complete, the connection between the calling customer and the previously selected outgoing trunk is established by the network control program 2.
It is set under the control of 22. By control of the data generated by the circuit control program 223, the outgoing trunk circuit of 103 is set to the appropriate state such that a response by the called customer is detected and the connection between the calling and called customers is established. communication becomes possible.

The status of the selected outgoing trunk circuit is then monitored by central processing unit 101 under control of supervisory trunk scanning program 213. When a response is detected by the called customer, the central processing unit requests execution of the response detection program 204, which controls the start of timing for billing purposes. If the customer hangs up before an answer is detected, indicating an unanswered or unacknowledged call, the central processing unit requests execution of a disconnect program 205, which The selected route is restored and the selected outgoing trunk in 103 is returned to a usable state.

Central processing unit 101 operates under the control of execution control program 203 and is responsive to a clock from clock 113 and uses this clock in connection with time records stored in memory.
Other signals are driven periodically to initiate execution of the appropriate program. This periodic signal is one of the functions controlled by the traffic recording program 220. It provides a means for initiating periodic functions such as traffic occupancy measurements. Periodically, the usage of the trunk being measured is sampled. Utilization is sampled, for example, over an hour, and trunks are sampled, for example, every 100 seconds. The utilization rate can be expressed as a value obtained by dividing the number of samples in which the trunk was occupied (number of times of use) by 36, which is the number of samples per hour.

Traffic recording program 220 is also used to control the cumulative number of attempts in trunk groups. Such counts are accumulated when the central processing unit under control of the digit analysis program 202 detects completion of dialing and calls the translation program 221 to control selection of the appropriate trunk group and trunk. After a trunk group and trunk are selected, central processing unit 101 jumps to the appropriate subroutine in the traffic recording program to increment the counter associated with the trunk group.

Finally, maintenance console message program 216 is executed when sending a message to or receiving a message from the maintenance console. When processor 100 indicates a potential failure, appropriate maintenance messages are sent to the console.

Extensive traffic measurements are commonly performed in telephone systems to operate the system efficiently, detect fault conditions, and provide design information for trunk group expansion. Traffic measurements are performed under the control of a traffic recording program.

4 to 13 show a program flowchart and memory arrangement for implementing the present invention in the switching equipment described in the previous paragraph. This includes detecting and counting unanswered calls in a trunk group, measuring individual members of the trunk group, reporting results to the maintenance console, and controlling monitoring of the trunk group from the maintenance console. The flowchart is shown connected to the prior art program described above with reference to FIG. The flowchart outlines the program that controls the following operations. Accumulation of trunk group counts of unanswered calls and individual trunks of unanswered calls for such groups (Figure 7); accumulation of number of usage attempts for each trunk of a group (Figure 8) ); Measuring the utilization of each trunk for a group (Figure 9); Printing unanswered call data for trunk groups and traffic data for individual trunks of a group (Figure 11); Monitored Automatic selection of trunk groups to be used (Figure 12); selection of such groups based on commands entered into the system (Figure 13).

FIG. 4 shows the memory arrangement required for the cumulative counts and measurements of the individual trunks of a trunk group being monitored. A monitored trunk group is a group of trunks for which the number of times the individual trunks are measured is thus accumulated. Each word contains three counters: one to accumulate the number of call attempts, one to accumulate the number of times the trunk was in use at the time it was sampled (Usage Count), and one to accumulate the number of times the trunk was in use at the time it was sampled. This is to accumulate unanswered calls. A block of memory has the capacity of n trunks,
the first trunk measurement occupies the first word;
The nth trunk measurement occupies the nth word. When an event is detected on the mth trunk of the group being monitored, the appropriate counter 141, 142 or 143 for the mth word is incremented.

For convenience in this particular implementation, such a block 14 is stored in memory within the switch equipment.
Only one 0 is used. This block 140
The address of the block may then be fixed as a parameter of the system, and the length of the block may take some convenient maximum value for a particular type of switching equipment, or the maximum length handled by such a system. A standard maximum value representative of the trunk group may be used. Alternatively, several such blocks may be provided to simultaneously monitor several trunk groups.

FIG. 5 shows a memory arrangement 119 of common variable data for trunk groups. This includes a memory 129 for counting the number of attempts to use the trunk in the group, a memory 128 for counting the number of unanswered calls in the group, and a threshold representing the normal maximum number of unanswered calls for the group. This is a memory 127 for holding.

FIG. 6 illustrates a storage arrangement for storing the identification number 139 of the trunk group being monitored and a flag 138 indicating that the group is being monitored for maintenance requests. When a call attempt or unanswered call is detected, a check is made to see if the event occurred on the trunk group whose number is stored in 139, and if so, the appropriate call is made in block 140 (FIG. 4). counter is incremented. This flag is maintained to distinguish automatically initiated trunk group monitoring requests from monitoring initiated in response to commands entered from the maintenance console 105. This will be further explained with reference to FIG.

FIG. 7 is a flow chart representing the program necessary to count unanswered calls. This includes the third
It includes the cutting program 205 and part of the translation program shown in the figure. When an unanswered call is detected by the conditional jump instruction represented by block 125 in disconnect program 205, translator program 2
Jump to subroutine 21. Block 1
Under the control of a program 221 represented by 26, data specific to this switching equipment, called translation data, is accessed to identify the trunk group identification number and the trunk group information associated with the trunk in which the unanswered call was detected. member number is read. Program 221 has been modified so that the central processing unit executes a jump instruction to subroutine 121 of unanswered call counting program 120. The unanswered call counting program 120 consists of subroutines 121, 123 and 124, and includes a counter 128 associated with a trunk group.
(Figure 5) and if the trunk group is being monitored, block 140 (Figure 4)
Increment the unanswered call counter for each individual trunk. Under the control of subroutine 121, unanswered calls for that trunk group are counted by counter 128. Next, subroutine 123 is executed, under whose control a comparison is made between the trunk group identification number or trunk group number and the number of the monitored trunk group stored in memory location 139 (FIG. 6). It will be done.
If the comparison results in a match, subroutine 1 is used to control the increment of the number of unanswered calls for that trunk by the central processing unit 101.
A jump to 24 is made. The member number of the trunk has previously been found under the control of the translation program 221, and if that number is m, then the number of unanswered calls of the m-th trunk is 14.
3 (Figure 4) is incremented.

Unanswered call data for various trunk groups can also be combined with similar data from other switching equipment. Data indicating that a number of systems are recording high rates of unanswered calls to and from a particular switch unit can be used to identify problems with common equipment in that system.

FIG. 8 is a flowchart of a program that measures the number of usage attempts of individual members of a monitored trunk group. This flowchart includes parts of the numerical analysis program 202, translation program 221, and traffic recording program 220 shown in FIG. Under the control of the subroutine 135 of the digit analysis program 202, when the completion of dialing is recognized, the translation program 2
20 subroutines 133 are called to control the selection of the appropriate trunk group and member numbers of available trunks within that group.
Subroutine 134 of traffic recording program 220 is then called to control the incrementing of attempt counter 129 for the selected trunk group. The traffic recording program 220 has been modified so that the central processing unit executes the jump to the individual trunk attempt count program. Individual trunk attempt count program 1
30 consists of two subroutines 131 and 132. Subroutine 131 is adapted to control checking whether the trunk group for this call is the same as the trunk group being monitored. Central processing unit 101
is the identification number of the selected trunk group and the identification number of the trunk group being monitored 139
(Figure 6). If a match is obtained as a result of the comparison, the central processing unit 101 executes a jump to subroutine 132 and executes subroutine 1.
Under the control of 32, the number of attempts 141 (FIG. 4) corresponding to the member number of the selected trunk is incremented. Then, or if the comparison results in a mismatch, central processing unit 101 jumps to traffic recording program 220, under whose control other traffic recording tasks are completed.

FIG. 9 shows a flowchart of the individual trunk measurement program 150. Central processing unit 101 accesses trunk group translation data 158 (FIG. 10) when executing this program. Trunk group translation data 158 is data 16 common to all members of the group.
Contains 5. Trunk group translation data 1
58 also contains identification numbers for all trunks in the group from the first member whose number is stored in location 159 to the last member whose number is stored in location 160. The trunk identification number is used to access data regarding the current status (empty) of each trunk. Do not confuse a trunk's trunk identification number with its member number. The member number is in the list in block 158 or in block 140.
It only corresponds to the position in the set of kakuntas in (Fig. 5).

The central processing unit 101 generates a signal approximately once every 100 seconds under the control of the execution control program 203. The execution control program 203 uses this signal to control the usage measurement program 15 of each trunk.
0 (FIG. 9) to perform a jump to the initial subroutine 152. Under the control of subroutine 152, the trunk group number stored in location 139 is read and used to access trunk group translation data 158 (FIG. 10). Subroutine 15
2, central processing unit 101 accesses data block 158, which in turn reads the number 159 of the first trunk in the group by executing subroutine 153. Under the control of subroutine 154, a check is made to see if the trunk is occupied, and if so, subroutine 155 controls the incrementing of the utilization counter in block 140 corresponding to that trunk. Central processing unit 101 then accesses the trunk group translation data under control of subroutine 156 to check whether there are any more trunks in the group. The identification number of the next trunk is read under the control of subroutine 157 by accessing data block 158, and subroutines 154, 155, 1
The loop consisting of 56 and 157 is repeated. This process ends with trunk identification number 16.
It continues until a zero is read, after which a loop check in subroutine 156 indicates that the individual trunk utilization measurement program 150 is complete. This allows the central processing unit 10
1 executes a jump instruction and returns control of the central processing unit 101 to the execution control program.

FIG. 11 shows the flow of a special traffic data printing program 163 for controlling the communication of data generated by executable programs 120, 130, and 150 (FIGS. 7-9) to maintenance console 105. It's a chat. Maintenance console message programs 216 are well known to those skilled in the art. The maintenance console message program 216 is modified to periodically send messages to the central processing unit 1.
01 is special traffic data printing program 16
It is now possible to jump to 3. Special traffic data printing program 163 includes two subroutines 161 and 162. Subroutine 161 locates locations 128 associated with each of the trunk groups in the switching system.
The data settings control the printing of the number of unanswered calls stored in (FIG. 5). Subroutine 162 sets data to control the printing of the contents of the counters in block 140 (FIG. 6) representing all attempted, utilized, and unanswered calls for trunks in the group being monitored. Control. The data set by various subroutines of the maintenance message control program 216 and then by a special traffic data printing program 163 is sent to the maintenance console 105.
to control printing. The program flowchart says that the data will be printed, but
Other forms of display and recording may also be provided, including the use of video terminals, recording in mass storage for later processing or display, and transmission of such data over large distances.

FIG. 12 shows a flowchart of the monitored trunk group selection program. The trunk of the group being monitored is counter 140 (FIG. 4).
Recall that it is measured individually using The function of program 170 is to select and later monitor trunk groups whose number of unanswered calls exceeds a predetermined threshold. Trunk group variable data 119 (Figure 5)
includes a counter 128 for counting the number of unanswered calls for the trunk group and a call store 127 for maintaining a threshold for the maximum number of successful such calls for the group. This threshold is predetermined as part of the translation information of the switching equipment. The threshold may be calculated automatically using an algorithm according to trunk group size, derived from a table that specifies the threshold as a function of group size, or changed by a message from the maintenance console. You may.

The central processing unit 101 generates a signal approximately once every hour under the control of the execution control program 203. The execution control program 203 has been modified so that the command to be executed is switched in response to this signal, and controls branching to the monitored trunk group selection program 170 (FIG. 12).
Initial subroutine 171 in program 170
5 accesses data stored in locations 127 and 128 (FIG. 5) associated with the first trunk group of the switching system. Under the control of subroutine 172, the two values are compared and if the number of unanswered calls 128 for the group exceeds the threshold 127 for the group, a jump to subroutine 174 is made by central processing unit 101. The group will be monitored for the next hour. A group is monitored when its identification number is written to location 139 by central processing unit 101 under control of subroutine 174. When the number of unanswered calls is less than or equal to that threshold, a test controlled by subroutine 175 is performed to see if more trunk groups exist, and if so, Traffic data for the next trunk group is accessed under the control of subroutine 173, which consists of subroutines 172, 175 and 173.
The loop of checking trunk groups is repeated to select the group to be monitored. The program 170 selects a trunk group,
Terminating when that number is recorded by subroutine 174 or a check controlled by subroutine 175 indicates that there are no more trunk groups at the station, subroutine 174 Alternatively, under the control of subroutine 175, central processing unit 101 then jumps back to the execution control program, and the execution control program controls subsequent operations of the central processing unit.

To handle cases where a station has a large number of poorly maintained trunk groups, the auto-initiated trunk group monitoring selection process should not always pick up the first failed trunk group. It is desirable to keep it. Thus, the selection process of program 170 examines all trunk groups, but changes the search to begin with a randomly selected trunk group or with the next trunk group of the previously monitored trunk group. This is desirable.

FIG. 13 is a flowchart of the console request monitored trunk group selection program 178 for allowing the selection of trunk groups to be monitored to be controlled by input messages from the maintenance console. This input message contains the identification number of the trunk group to be monitored. Maintenance console message program 21
6 has been modified to identify a new message type to represent this input message. Identification of this message type causes a branch to the console request monitored trunk group selection program.

The program 178 has two subroutines 176.
and 177. Subroutine 176
is necessary to recognize the details of a new type of message that represents a request to monitor a particular trunk group. Under the control of subroutine 176,
Subroutine 177 is called to control the initiation of monitoring by writing the trunk group number to location 139 and setting maintenance required flag 138 (FIG. 6). Under control of subroutine 177, a branch is made to return control to maintenance console message program 216, which controls processing of the next input message.

By setting the maintenance request flag 138,
Priority is given to maintenance requests over automatically generated requests. This flag is cleared when a trunk being monitored by a maintenance request is no longer monitored. When the flag is set, priority is given to requests from the maintenance console, so the trunk group will not be monitored as selected by the monitored trunk group selection program 170 (FIG. 12).