Meinberg DCF77C51 - Manual (Page 18)

18
Usage of the Current Loop Interface
The current loop interface can be wired to work in one of two modes: active output
drives passive input, or passive output to active input.
Active Output to Passive Input
If the clock's current loop output shall be wired to operate as active output, a
connection from the pin labeled +pass_out to Vcc (+5V) must be provided. The pin
labeled -act_out is pulled down to the auxiliary -15V supply, which must be made
available by the user.
active current loop output with auxiliary -15V supply
If an external -15V supply is not available, the -act_out signal can be connected
directly to GND, as shown below:
active current loop output without auxiliary -15V supply