The CM491 series Tek-Guard™ entrance panel is a directory style panel, for use with most open-voice (loudspeaking type) apartment intercom stations, up to a 20 button capacity. CM491 panels are equipped with a weather-resistant mylar cone speaker protected by a louvred style aluminum speaker grille, and solid aluminum pushbutton plungers with apartment markings permanently engraved, to resist vandalism. A built-in mini alphabetical directory module makes finding the tenant's pushbutton very easy. CM491 series panels are available for 4,8,12,16 or 20 buttons. For larger buildings, use our CM492 series modular style loudspeaking panels. All CM491 modules have a 45-ohm speaker and 4-20 buttons (in multiples of 4). All CM491 modules include a 20-name capacity mini directory which installs into the frame, above the speaker/button portion of the module. Directory strips can easily be inserted into the directory module using optional engraved plastic directory strips (model #TDS) and fill-in directory blanks (model #TDS-B). CM491 modules must be installed into an OF291 (flush) or OF291S (surface) panel frame. Flush CM491 panels require an OH191 flush housing. Surface CM491 panels do not require a backbox.