Input/output module adjustment


Estimated executing time: 0,5 hours.

For the input/output module good signal-to-noise ratio and drive capability are extreme important. Therefore execute the following steps carefully.

First of all temporary bridge G-H and I-J on the backplane to perform the following steps:

Carrier input

The carrier input volume potentiometer is followed by a preamplifier with a fixed gain of approximately x10.

A steady waveform should be applied to the line input, e.g. a 440 Hz 0,77 V RMS sinewave is ideal to check the carrier preamplifier. Turn down to speech input potentiometer and set the carrier input potentiometer to maximum. Connect CH1 of an oscilloscope to pin B on the right side of the backplane.

You'll get the following result (peak-to-peak + 15 V RMS):

Speech input

The speech input volume potentiometer is followed by a preamplifier with a adjustable gain between x1 till x1000 for any input sensitivity between 7,7 mV and 7,7 V. The input impedance is 10 kOhm and in practice microphones with allmost any impedance can be used.

To use a line output as speech input apply the same signal as used for the carrier to the speech input and set the speech input potentiometer to maximum.

Connect CH2 of an oscilloscope to pin A on the right side of the backplane. Adjust P16 until both signals are allmost equal (peak-to-peak + 15 V RMS):

Now your speech input has been calibrated for using line levels.


Don’t forget to remove both temporary bridges on the backplane.

Well done

Congratulations, you have now finished the input/output module adjustments, click here to navigate back to the assembly & adjustment instructions.


The contents of this document are provided as-is. The published information could contain technical inaccuracies, typographical errors and out-of-date information. This document may be updated or changed without notice at any time. Use of the information is therefore at your own risk without any liability for special, indirect, incidental or consequential damages resulting from or related to the use of this document.