ALWAYS inform us of the system you have, DK16, DK424, CIX28, CIX100, etc.

You can use ONLY certain circuits on each different control unit for door phones.

Here is some info from a DK installation manual:

1. DK40i and DK424: connect PDKU circuit 5 (T/R and PT/PR) to the DDCB HKSU modular
jack (see Figures 10-9 and 10-10).
DK14: connect applicable digital telephone circuit (logical port 02 or 03) to the DDCB KSU
modular jack. See Figure 10-7 and Figure 8-1.
2. Connect the door lock wire pair to the DDCB modular B-jack (pins 3 and 4).
3. Set SW1 to the DOOR position.
4. Set SW2 to the LOCK position.
5. SW3 inside the DDCB can be set to open or close the door lock relay whenever a door lock
button is pressed: if SW3 is in the “1-2” position, the relay closes when the button is pressed;
if in the “2-3” position, the door lock relay opens when the button is pressed.
Note SW3 comes from the factory in the “1-2” position.
6. In Program 77-1, set the door lock activation for three or six seconds and enable the PDKU or
RDSU ports for DDCB connection.
7. In Program 77-2, enable the DDCB B-jack for door lock operation.
8. In Program 39, assign door lock buttons to stations per the customer’s record sheet.
9. Check each telephone door lock button from each station: the DDCB modular B-jack (pins 3
and 4) will momentarily open or close (three or six seconds) when the button is pressed.

THE Bracha, old blond specialist in Rube Goldberg solutions.