Spec Sheet Preview: The Alpha Communications® 931 amplifier/power supplies are used with the 870W, 8870 and 902 series handset intercom stations (or equivalent), to provide intercom amplification, power to operate the electric door opener(s) etc., and power to signal the handsets from the lobby entrance station. The 931 units each require a standard 120VAC power source. These 931 amplifier/power supplies are designed to easily surface mount right onto the finished wall by means of customer supplied screws. Connection …