Spec Sheet Preview: The BLM333 series speaker/microphones are designed to be used only with Alpha Communications® / S.T.R.™ QwikBUS™ modular series door entry stations. The BLM333 series is used with the 2-wire (loop) type QwikBUS™ apartment handset intercom stations, open voice apartment intercom stations and/or video monitor stations with handsets or open voice style. All BLM333 speaker/microphone modules feature a weather-resistant speaker, long-life electret condenser microphone, illuminated dry-contact low voltage light push button and plug-in connector for easy wiring …