1A2 is a designation for a generation of multi-line "key" telephone systems developed by Bell Laboratories and manufactured by Western Electric for installation by local Bell telephone companies.
It was the successor to 1A and 1A1 phone systems, and the end of "electromechanical" phone system development in the United States. After 1A2, phone systems were electronic, then digital, and then IP.
AT&T licensed its 1A2 technology to other manufacturers. Compatible and nearly identical equipment was made by ITT (later Cortelco), Stromberg-Carlson (later Comdial), GTE (later Verizon), and Northern Telecom (later Nortel).
A wide range of compatible phones, accessories and replacement parts was made by other companies.
1A2 is a "classic" technology. Millions of 1A2 phones were made and many of them are still in use.
Although they lack the features of 21st-Century phone systems, 1A2 performs the basic telecom tasks reliably, year after year after year.