The CM492 series Tek-Guard™ entrance panel is a modular style panel, for use with most open-voice (loudspeaking type) apartment intercom stations. CM490 panels are equipped with a weather-resistant mylar cone speaker protected by a louvred style aluminum speaker grille, and solid aluminum (black anodized) pushbutton plungers with apartment designations permanently engraved, to resist vandalism. Alphabetical directory modules make finding the tenant's push-button very easy, even in larger buildings. CM492 series panels are available with a variety of module and frame/housing configurations. Modules beginning with the model CM490 are button modules only, with no speaker. CM490 modules are available with 4 to 80 buttons (in multiples of 4). Modules beginning with the model CM492 have a 45-ohm speaker and can accomodate 4-60 buttons (in multiples of 4). For modules requiring a speaker only with no buttons, use model #AM492. Directory strips can easily be inserted into the model #AM190D (60-name capacity) directory modules using optional engraved plastic directory strips (model #TDS) and fill-in directory blanks (model #TDS-B). CM490, CM492, AM190D and AM492 modules must be installed into a flush or a surface panel frame. Flush panels require an OF190 series frame, with the OH190 series flush housing. Surface panels require an OF190S series surface frame only, and do not require a back box.