When using the C8137 Transmitter Interface with the C601 Encoder, the C8137 introduces voltage into the C601 via input zones on the C601. There is a component on the C601 that protects the microprocessor from any type of stray voltages.
When the C601 detects any stray voltage it causes the microprocessor to reset in order to protect itself. The voltage output from the C8137 is enough to cause this. It is recommended that a 1K resistor be placed in series on the zone input for each zone on the C601 that is being used. This will limit the amount of voltage that reaches the C601 allowing it to function normally