142 / 266 3CIRCUIT DESCRIPTION
in every situation.
The voltage occurring in the simulation is proportional to the current and is compared in the operation
amplifier IC14 functioning as a comparator to the maximum permissible value that is prescribed and
adjustable via the resistor divider R22 and TP1. The signal for switching over the relay REL 2 is present at
the BF / CF output.
Footswitch input circuit
The footswitch is operated at a DC voltage of 15 volts via a multipole line. Since the footswitch connection,
due to its length of up to several meters, can also function as a receiving antenna and absorb interferences,
an RC low-pass is connected directly to the input sockets of the ICC which severely dampens high interference
frequencies. The footswitch signals are then regenerated using the buffer IC 13.
For further processing in the processor, the output signals from IC 13 are adapted to the TTL level of the
processor. To do this, the noninverting buffer IC5 is used.
Further signals are converted in the same manner from 15 volt CMOS level to the TTL level in the buffers
IC1 and IC6.
Motherboard
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