Remote reading system for electricity meters - uses phase and duration modulated IR light from LED's to exchange binary signal information

摘要

The system is used for automatically reading an electricity meter, using a rear infrared binary encoded signal. A level one and zero are identified by a double modulation, both in phase and in duration. The light source is associated with the meter and is controlled by a microprocessor in circuit with a RAM and a clock, establishing the time base. The data to be transmitted are fed into the RAM in a predetermined format by the microprocessor. The frequency and amplitude of the signal is determined by a current amplifier, having its supply current controlled by the microprocessor. The output of the amplifier feeds an assembly of gallium arsenide diodes which are connected in cascade. When a logic one is to be transmitted, the microprocessor awaits an interruption, applies a validation signal to an AND gate to enable the amplifier counts two interruptions and then blocks the 01Duntilthefollowinginterruption.