Viking Door Entry Control for 4 Entry Phones, Provides CO Sharing, Call Waiting, and One Aux Contact Allows an entry phone to share a single telephone line with a residential or business telephone system House phones ring with C.O. line cadence or distinctive ring when the entry phone “Call” button is pressed Compatible with these Viking entry phones E 10, E 20A, E 30, E 40 Handsfree Phones K 1500 7 Stainless Steel Panel Phone Or use with any analog touch tone phone Provide entry phone activated chimes and whole house paging when used with Viking model SLP 1 Produces double “Call Waiting” tones One set of normally open and normally closed contacts available for operating a doorbell, camera, lights, etc. Add door strike capability with the Viking model RC 2A Remote Touch Tone Controller