Transmission system

A simplex information transmission and display system, comprising:

• a control unit for generating data relevant to said information;
• an electric lighting system that is in the environment where said information is to be displayed and that has an a.c. power supply;
• a modulator connected to the power supply for said electric lighting system and to said control unit, to phase modulate the power supplied to said electric lighting system with a signal having a frequency on the same order of magnitude as said power supply and containing address information and said data, to thereby transmit data and address information at regular intervals to each module via light emitted from said lighting system;
• and
• a plurality of discrete modules located remote from said control unit and in the environment of said lighting system, each having a self-contained power source for supplying operating power thereto, a photodetector for detecting the data and address information transmitted via said light, an LCD display for displaying the detected data, and a timer for timing the interval between receipt of successive transmissions of a particular address, said timer being adjustable to a predetermined time setting and in the event that said address is not received within said predetermined time said module being adapted to visually signal a possible error in the module by flashing its LCD display.