1A2 Key Telephone System

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The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System.

The 1A2 Key Telephone System is a modular system that provided flexible solutions for a variety of telephone service requirements. It provides multiple users with control over multiple telephone lines without the requirement for an operator, system attendant, or receptionist. Each user can select a specific telephone line to place calls on, or to answer calls, and manage those calls by placing them on hold or transferring them to other stations. The system provides options for station-to-station signaling and intercom, and music-on-hold. The control functions are operated directly on each telephone instrument with a set of push buttons (keys) that have lamps installed internally to provide visual indication of line status.

Introduced in 1964, the 1A2 system represents a stage of key telephone systems development at Bell Laboratories that started in the late 1930s with the 1A Key Telephone System, and was an improvement over the 1A1 system introduced in 1953.^[1]

Compatible 1A2 equipment was manufactured by competing vendors, such as Northern Telecom, Automatic Electric (GTE), ITT, and Stromberg-Carlson. The successor technologies to the 1A2 Systems include the AT&T Merlin, AT&T Spirit, and AT&T Partner systems.