Junction box for door answer-phone system - with LEDs indicating state of primary and secondary transformer voltages

摘要

The junction box simultaneously provides AC and DC operating voltages. It incorporates opto-electronic display elements (2,3) e.g. LEDs coupled across the voltage taps of a transformer and visible through an opening (7) in an overlying fuse board (5), in turn enclosed by a hinged cover plate. The latter is pref. of transparent material and incorporates an integral lens (4) aligned with the opening (7) in the fuse board (5). Pref. the junction box is connected to the mains to provide a 12 Volt AC supply and 8 Volt and 12 Volt DC supplies. The LEDs (2,3) indicate the state of the primary voltage, the AC voltage for the bell circuit and the door release circuit and the DC voltages for the speech and control circuits. Pref. each LED is illuminated if a reference voltage is exceeded.