The A 4500B is a weekly timer and Evacuation controller all housed in a convenient 1RU rack mount chassis. A total of 50 “event” switching times are available through the timing functions. Each event can be set to turn on any single day of the week or on multiple days, from 1 sec up to 24 hours. When a timing event is activated, an MP3 audio file will be played and output through the dual RCA line level output. There are fourteen MP3 playback options for the timing events, which include the Bell, Prebell, Music and folders 5-15. A micro SD card which is supplied, houses all the MP3 files to be played as well as storing all the timing events (Note: MP3 files should have the following specifications for optimum performance. 128kbps, 44.1kHz, 32bit, VBR or CBR, stereo or mono).