Abstract: An electronic device has a circuit whose operation is adjustable by changing a variable component responsive to stored data. The electronic device also has a processor responsive to a stored program for controlling the circuit by receiving new input data and changing the variable component by replacing the stored data with the new input data. Preferably the electronic device has radio frequency circuits for transmitting and receiving a radio frequency signal, and audio frequency circuits for relaying and reproducing an audio signal. For calibration and adjustment during assembly or servicing, the electronic device is connected to automatic testing, checking and adjustment equipment including a computer that provides the input data to change the variable component as required. The calibration or adjustment is made as a series of progressively better approximations to the required valve.