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RTU-292 Operations Manual
Figure 6-1 Hybrid Balance Test Set-Up
6.5.2.1 Main Hybrid Test Procedure
1. Disconnect the RTU-292 from all other equipment and connect the test equipment as shown
in Figure 6.1.
2. Set the PSTN levels for -9 dBm using Option SW2-1, -2, and -3.
3. Start with the following pushbuttons OFF: TEL LINE/PHONE, TEL LINE/RADIO, and
TEL VOX. The positions of the other buttons are unimportant. Place the RTU-292 in set-up
mode by setting SW2-7 ON and then turning on the power. (See paragraph 2.10.1 for further
details about set-up mode.)
4. Adjust the TX Level Adjust, R133, so that the audio voltmeter reads -6dBm (0.387V rms).
This sets the transmit signal output path in the RTU-292 for unity gain if the input level is
correctly set.
5. Adjust the RX Level Adjust, R116, so that the PEAK LED flashes rapidly and is on about
50% of the time. (This is different from the instructions in paragraph 2.10.3, which set the RX
Level Adjust for voice)
6. Remove the unit from Set-up Mode by turning the RTU-292 Main Power OFF, setting SW2-
7 OFF, and then turning the main power back ON.
7. Push the TEL LINE/RADIO button to start the adaptation cycle.
8. When the initial adaptation cycle is complete, the noise output can be read on the audio
voltmeter. The voltage should be less than -37dBm (10.9 mV). The trans-hybrid loss is the
difference between this reading and the approximate -7 dBm noise level.
JPS Communications, Inc.
6-21