2 Button. This Videx 3101 full base audio phone has an AC buzzer input, adjustable electronic call tone, a door open push button and a spare service button. It is suitable for use on traditional 4+1 audio systems that require an AC buzzer call or an electronic call tone including the 4k series, 8K series, VR4K series and VR120DK series kits.. Spare service button. AC buzzer call. Door release facility. White finish