4000 Series button expansion modules are used to achieve the required amount of call buttons for audio or audio / video door entry systems. Modules are available with 2, 3, 4 and 5 buttons. Double button modules are also available with 4, 6, 8 and 10 buttons, where 2 buttons share the same name plate window. There are two variations of button modules available depending on the 4000 series audio or audio / video system being installed. 4842 Up to 4845 and 4842D up to 4845D for audio or audio / video 4000 series modules without the built-in IDC connector. Each module has a terminal connection that houses 2 terminals for each button where the buttons, depending on jumper settings, can have a common terminal or each button can have its own common.