The C-500 allows single line telephones or a telephone system to share a phone line with two Viking entry phones. Up to four C-500's can also be connected in series allowing control of up to eight entry phones and / or door strikes. Tenants may answer an entry phone call, converse with the visitor and let them in with a touch tone command which activates one of two relays to control a gate or door strike.

The C-500 also has a built-in five number dialer to call your cell phone or an outside line if there is no answer on the inside phone. If the outside call is busy or ring no answer, the C-500 can call up to four more numbers.

The C-500 provides the house phones with user programmable entry phone "Caller ID". Tenants may also call the entry phones for monitoring purposes or enter touch tone commands to activate, deactivate or toggle the door strike/gate relays.

The C-500 allows up to 6 permanent keyless entry codes, 2 "one time use" entry codes and 1 toggle entry code for each door. The C-500 provides optional entry phone distinctive ring, two trigger inputs for "Request to Exit" and field programmable Caller ID or beep tones when answered to indicate which door is activated.