9 ELECTRICAL COMMUNICATION AND CONTROL EQUIPMENT, NAMELY TRANSMITTERS, RECEIVERS, ENCODERS AND DECODERS, CONTROL AND STATUS REPORTING UNITS, DIGIT MESSAGE DISPLAYS, COMPUTER INTERFACE UNITS, STATUS REPORTING AND ALARM UNITS, OPTICAL INPUT CARDS, VOLTAGE INPUT CARDS, VOLTAGE SENSING CARDS, ADDRESS, LOGIC AND RELAY MODULES, DIGIT MESSAGE DISPLAY PANELS, FILTERS, AMPLIFIERS, MOUNTING PANELS, REMOTE CONTROL UNITS, AND REPEATER PANELS