Causes and handling of program-controlled switch external Line Disconnection (1)

1 Introduction

At the end of 1992, the tianhushan Mining Bureau introduced the SOPHO-S1000 of Time-controlled user telephone switch produced by Philips in the Netherlands. In the early stage, 304 telephones were installed, and 18 trunk lines were purchased from the post office and put into use at the end of the same year.

The performance indicators of the program-controlled switch are normal, but the switch experienced a special fault in the recent period: the external line, especially the remote call outside the province, is called internally, and the switch is automatically dropped, the probability is about 20%, which greatly reduces the success rate of external dialing.

2. Fault Analysis

2.1 Analysis of relay routes

The analysis shows that the call may be dropped because the contact resistance of the relay wires may be too large due to oxidation. The author carefully handles each cable connector of the trunk line. Ensure that the contact resistance is minimized, and the signal of each relay is measured normally when the disconnects block on the switch side, but the disconnection has not improved.

I speculate whether it is because the caller uses a portrait phone that can only be used for pulse dialing and cannot send dual-audio signals). However, I carefully analyze and query the local post office that is prone to disconnection, it is found that the other party has adopted the program-controlled exchange, and both of them can send dual-audio signals. There is no horizontal phone number, so this speculation is denied. Next, the author analyzes whether the cause of the fault is in the trunk line itself. After careful analysis of the trunk line characteristics and address table, see table 1), it is found that all the relay are two-way relay. Two-way relay has a fatal weakness, that is, the priority of the two-way relay is not high. During the traffic peak, some phones will be disconnected due to tight relay.

Table 1 trunk line address, route, and characteristics table trunk line number relay characteristics hardware address routing number disconnected block location into voice board no voice board location

3982101 bidirectional 12403 0300 2905 Y 4303

3982102 bidirectional 22403 0301 3405 Y 4307

3982103 bidirectional 02403 0302 1405 Y 4403

3982104 bidirectional 02404 0303 1404 Y 4402

3982105 bidirectional 02405 0304 1403 Y 4401

3982106 bidirectional 22401 0305 3407 Y 4405

3982107 bidirectional 22400 0001 3408 Y 4305

3982108 bidirectional 22402 0306 3406 Y 4308

3982109 bidirectional 12404 0309 2904 Y 4303

3982110 bidirectional 12401 0307 2907 Y 4306

3982111 bidirectional 02402 0308 1406 Y 4404

3982112 bidirectional 02400 0311 1408 Y 4406

3982113 bidirectional 12400 0005 2908 N

3982114 bidirectional 12402 0310 2906 N

3982115 bidirectional 22404 0109 3404 N

Table 2 trunk line address, route, and characteristics table trunk line number relay characteristics hardware address routing number disconnected block location into voice board no voice board location

3982101 single entry 12403 0300 2905 Y 4303

3982102 single entry 22403 0301 3405 Y 4307

3982103 single entry 02403 0302 1405 Y 4403

3982104 single entry 02404 0303 1404 Y 4402

3982105 single entry 02405 0304 1403 Y 4401

3982106 single entry 22401 0305 3407 Y 4405

3982107 single entry 22400 0001 3408 Y 4305

3982108 single entry 22402 0306 3406 Y 4308

3982109 Single Output 12404 0309 2904 Y 4303

3982110 Single Output 12401 0307 2907 N

3982111 Single Output 02402 0308 1406 N

3982112 Single Output 02400 0311 1408 N

3982113 Single Output 12400 0005 2908 N

3982114 Single Output 12402 0310 2906 N

3982115 Single Output 22404 0109 3404 N

For example, the peak hours are from to on Monday ~ ) Traffic test showed that the ratio of incoming and outgoing relay traffic was about 52%: 48%, and the total number of existing relay lines was 15, therefore, the author sets the ratio of inbound and outbound relay to, that is, 8 is selected as single-Inbound relay, and 7 are used as single-outbound relay. In this way, the overall traffic volume is balanced, it can also maximize the use of existing trunk line resources.

After the number of incoming relay entries is determined, how can the incoming relay be better connected to the switch? Considering that the contact and communication number previously announced by our Bureau is 3982101, if we change the relay number again, it will cause a lot of inconvenience to users. After comprehensive consideration, the author decided to use the 3989201-centered automatic cycle connection and selection method, that is, 3982101-3982108 trunk lines, automatic cycle connection and selection. When an external line calls 3982101, as long as one of the eight relays is idle, the switch automatically finds and occupies this relay, which greatly facilitates external users.

After the solution is determined, the author goes into one system to determine the specific operation steps:

1) notify the Post Office in writing and apply to change all two-way relay to one-way relay, that is, the single-entry relay is: 3982101 ~ 3982108; single-out relay: 3982109 ~ 3982115; and all inbound relay are required to provide the Automatic loop connection and selection function.

2) After the relay feature of the Post Office is modified, modify the route number of the trunk line accordingly. We define the route number as 03. ** the outbound Route number is 00. ** to analyze and compare the relay feature table, we must set the original 03. ** change the single-out relay route to 00. ** routing, that is

3982109 of the 03.01 route is changed to 00.01; 3982110 of the 03.07 route is changed to 00.07;

3982111 of the 03.08 route is changed to 00.08; 3982112 of the 03.11 route is changed to 00.11;

3982114 of the 03.10 route is changed to 00.10; 3982115 of the 03.09 route is changed to 00.09.

You can modify the relay route number on the maintenance terminal of the switch and find the 3982110 hardware address EHWA. The value is 12401. Run the OM command 7014 to define the hardware address 12401 as the 00.07 route, activate EHWA and set it to the installation status.

The modified trunk line routing features are shown in table 2.

In this way, the PE of the switch engineering file is modified, so that the switch can properly manage the signaling of the outgoing and incoming switch relay.

After several days of detailed observation, it was found that the automatic disconnection from the external line had improved, but it still occurred from time to time.