INTERPHONES; TELEPHONES; KEY TELEPHONES; RADIO TRANSMITTERS AND RECEIVERS; TELEVISION TRANSMITTERS AND RECEIVERS; VEHICULAR RADIO COMMUNICATION UNITS; MARINE RADIO COMMUNICATION UNITS; AIRCRAFT RADIO COMMUNICATION UNITS; TRANSCEIVERS; AUTOMATIC TELEPHONE EXCHANGES; MAGNETIC TELEPHONE EXCHANGES; ELECTRICAL KEYS FOR TELEPHONES; SOUND AMPLIFIERS; DIALS; CONNECTORS; CONVERTERS; RELAYS; ELECTRICAL KEYS; SWITCHES; FACSIMILE TRANSMITTERS; PHOTOTELEGRAPHIC APPARATUS; REPEATING EXCHANGES; DATA SIGNAL ...