IBM 1750 Switching System

The IBM 1750 is a stored program, microprocessor controlled PABX introduced in the late 1970's. The analogue switching network uses thyristor cross-points. The system can be expanded from a minimum of 100 extensions to a maximum of 760 extensions (96 exchange lines) in modular stages. In addition to supporting modular hardware expansions, the system software provides separate feature packages and function sets.