The vandal-proof stainless steel housing and call button go outside where it can be accessed by someone in a wheelchair. See this article for mounting requirements: Americans with Disabilities Act (ADA) Intercom and Telephone Mounting Requirements
The master station goes inside and can be wall or desk mounted. There is a door release button on the master station that could be used to activate an optional electric door opener for remote door opening.There is a call button on the outside unit that will sound a ring tone on the inside master station. The master station presses a Talk button whenever its user wants to talk, but the outside unit does not have to press a button to talk.
Select a row below to filter reviews.