When using the C8137 with the C601 encoder, the C8137 puts voltage into the encoder. This is normal. There is a component on the encoder that protects the microprocessor from any type of high voltage such as lightning or voltage spikes. When the voltage protector senses any type of high voltage or current, it causes the microprocessor to reset.
When connecting a C8137 interface to a C601 encoder, Bosch recommends that you install a 1 K resistor in series on the input side of the loop you are using. This limits the voltage and current through the loop, which is connected to the C601 encoder zone. This will prevent the microprocessor from resetting when using a C8137 module with the encoder