Receivers

Receivers are typically small and designed to be integrated either into a lamp post or a meter/breaker panel. The original ones were completely electromechanical and driven by synchronous motors, later receivers use a microprocessor to do the protocol decoding and any other special functions. The early electromechanical receivers use a capacitor in series with the coil of a reed relay to form a tuned LC circuit with the same frequency of the transmitter, the reed relay operates when a signal is present. The first electronic receivers also used a LC filter circuit but monitored the signal presence with an analog-to-digital converter instead, the latest receivers use digital signal processing to detect the signal entirely in software. Most receivers will use bistable relays for their outputs, these relays have two coils in them and will stay in either position without any power being applied, a pulse on either coil will set which position the relay is in. Many receivers use capacitive dropper circuits for their power supplies alongside a large buffer capacitor, they barely draw any power as they only need to apply power to the relay when actively changing which position it is in.