Meinberg DCF77C51 - Manual (Page 19)

19
Passive Output to Active Input
If a current loop output shall be wired to operate as passive output, the input wust be
wired to operate as active input. A connection from the pin labeled +pass_in to Vcc
(+5V) must be provided. The pin labeled -act_in is pulled down to the auxiliary -15V
supply, which must be made available by the user.
active current loop input with auxiliary -15V supply
If an external -15V supply is not available, the -act_in signal can be connected
directly to GND, as shown below:
active current loop input without auxiliary -15V supply