Troubleshooting Of Telephone Exchange

- Jun 14, 2018 -

General steps and procedures for troubleshooting and troubleshooting:

The first common fault:

polarity - switched telephone : It feeds the 48 V DC feed on the outside telephone line to the inside of the phone and gets the correct polarity . This part of the circuit is damaged .It is usually caused by improper connection (such as the damage caused by wrong access to the city electricity 220) or lightning strike. The common way of damage is, four diodes break short circuit, or open circuit, lightning protection element break down, or break the circuit, current limiting resistance or inductance break. The malfunction is that the phone does not respond to the line, as if it were not connected, or if it has a dialing tone, then a busy tone, and finally whines, as if the phone had not been put in place. At this time, we can judge by the method of multiplex meter checking resistance, measure the added voltage if necessary, and carry out the soft breakdown measurement of this part of circuit.

The second common failure:

The telephone switch, that is, the spring switch circuit, acts as a telephone hook and internal circuit conversion function, and its failure is as follows:

1. You can't get off the plane, that is, you can't answer the phone.

2. You can't hang up, the phone's always like you can't hang up.

3. In the course of the call noise appears, after the removal of the aircraft, hands-free loudspeakers also appear voice calls.

4. There are some inexplicable faults that cannot be determined by conventional methods. At this time we may as well change this small switch, sometimes has the unexpected effect yo. I have encountered such a telephone with no telephone number. After receiving the malfunctioning machine, I connect the line, the screen shows normal, after picking up the handle, the hands-free function is also turned on, and the dial tone can be heard. During the dialing test, the voice of which code to retransmit is very loud, but the telephone exchange cannot recognize the dual audio code issued by the telephone. When blowing into the receiver and conducting self-test, the telephone is found to hang up automatically, then remove the machine, and then hang up again and again, so it is repeated. I have carried out several such tests. For the last time, I did not carry out a dialing test. Instead, I carried out a self-test of blowing air. I carried out the phone sending and receiving tests. All of a sudden, I heard someone in the receiver talking and asked where and who I was looking for. After I answered, I asked where the other person was, and he told me that he was a user of the local virtual network. During this period, the phone sent a pulse code, and when it was unplugged, it found that there was no damage to the circuit.This kind of fault can be said to have several related circuits, just like people who have cancer, they have replaced this small switch, ha, they have even recovered. It seems that this small switch not only has a high loss rate, The malfunction caused by it is also very strange.

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