A system for testing and calibrating communications equipment or modules. A processor is configured to perform a test or calibration procedure on a communications unit under test (UUT) in response to commands entered by an operator. Test and measurement instruments arranged to be responsive to the computer include a power supply for activating selected portions of signal paths in the UUT, one or more signal generators, and one or more instruments for measuring output signals produced by the UUT in response to the test signals. The UUT has switches and terminals for inputting test signals from and returning output signals to the instruments, and an adapter is connected between the processor and the UUT. When performing a calibration procedure, the adapter operates the switches and connects the terminals on the UUT to the test and measurement instruments under the control of the processor.