Ummm, lets see. (Goes to the Viking site.) Yup, looks like it is only for use with a CO port. Make sure the talk battery is "on".
You probably got this with the unit but what the heck-
https://www.vikingelectronics.com/products/pdf/c-1000b.pdf Question is why are you using that thing and not the Partner doorphone? Partner doorphones do connect to extension ports. Has to be cheaper than that Viking controller and doorbox. Makes no sense unless you have a system that doesn't support doorphones or needs more than two.
You can use the contact closure if you need to control up to 2 door strikes.
-Hal
