Spec Sheet Preview: The DTSM series speaker/microphones are designed to be used with Alpha Communications® / S.T.R.™ digital-dial modular series door entry stations. The DTSM series is used with the 2-wire (loop) type ReliaBUS™ apartment handsets (i.e. HT3011, HT2011) only. All DTSM 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. All …