ST 500 "Piranha" Operation Manual: Use Guidelines
69
9.4.1. SEARCH FOR ACTIVE MICROPHONES IN AN ANALOG TELEPHONE LINE
The initial state:
1. The tested telephone line consists of 4 wires.
2. The cable is equipped with a 6P4C plug.
3. The consumer device is an analog telephone.
4. The two central connector pins are used by the telephone.
5. PBX' operation voltage is 26 V.
6. The line operates normally, with the telephone connected to it.
Search algorithm:
1. Connect ST 500 to the telephone line according to the scheme 3B (fig.25) or 3D,3E (fig.26).
2. Turn on the test sound source.
3. Turn on the ST 500, activate "LOW FREQUENCY AMPLIFIER" channel.
4. Press "FUNC" (turn on "ELECTRONIC SWITCH SETTINGS" mode).
5. Press "F3" to select 6P4C connection, The scheme is shown in
6. Press "FUNC" (turn off "ELECTRONIC SWITCH SETTINGS" mode).
7. Press "F2" and set maximum gain (x100).
8. Connect the headphones to the main unit and adjust the sound volume.
9. Press "F4" (turn on the AUTOMATED mode).
The device will start iterating through all possible combinations of wire pairs. The tabular
cursor moves through the table, stopping for a few seconds on the tested combination of wire
pairs. At this time, the operator can listen to the received signal. After going through all the
possible combinations, the scan will stop.
Possible testing results and their interpretation:
Case 1
Pair 3-6
There is no voltage. The test sound
cannot be heard in the audio output.
No dynamic microphone is detected. An
electret microphone may still be
connected, that had no power supply at
the time of testing. A bias voltage check
(9.4.2) is required.
Pair 4-5
The voltage is DC 26 V.
The test sound cannot be heard in the
audio output.
Case 2
Pair 3-6
There is no voltage. The test sound can
be heard in the audio output.
Either a dynamic microphone, or an
electret microphone with independent
power supply (possibly, from the
telephone line) is connected. The
microphone must be located.
Pair 4-5
The voltage DC 26 V. The test sound
cannot be heard in the audio output.
Case 3
Pair 3-6
The voltage is DC 3-20 V. The test sound
can be heard in the audio output.
An electret microphone is connected,
with "phantom" power supply through
wires #3 and #6. The microphone must
be located.
Pair 4-5
The voltage DC 26 V. The test sound
cannot be heard in the audio output.
