Nortel Networks RTU-292 - Manual (Page 89)

RTU -292 Operations Manual
6.5.3 VOX SENSITIVITY MEASUREMENT
The following test procedure measure the sensitivity of the VOX in the RTU-292. This is the
amplitude of the incoming signal from the telephone line required to trigger the VOX.
Figure 6-2 VOX Sensitivity Test Set-Up
6.5.3.1 VOX Test Procedure
1. Disconnect the RTU-292 from all other equipment and connect the test equipment as shown
on Figure 6.2.
2. The PSTN level setting must be known. To determine this, remove the top cover and note
the positions of SW2-1, -2, and -3.
3. Start with the following pushbuttons OFF: TEL LINE/PHONE and TEL LINE/RADIO.
Push the TEL VOX button ON. The positions of the other buttons are unimportant.
4. Set the audio signal generator frequency to 1 kHz with an output amplitude of less than -
40dBm (7.7mV rms).
5. Push the TEL LINE/RADIO button to start the adaptation cycle.
6. When the initial adaptation cycle is complete, slowly increase the audio generator amplitude
until the Keyed LED on the RTU-292 comes on. The audio generator amplitude at this point
(read directly by the audio voltmeter) is the VOX sensitivity. The VOX trip point is dependent
on the setting of the PSTN levels and the VOX sensitivity setting. It should be 16 + 2 dB
below the PSTN setting as listed in the table below:
VOX Sensitivity
VOX Trip Point
MAX 19 + 2 dB below the PSTN setting
MED 16 + 2 dB below the PSTN setting
LOW 13 + 2 dB below the PSTN setting
MIN 10 + 2 dB below the PSTN setting
JPS Communications, Inc. 6-23