Abstract: A passive transponder for identifying objects remote to an interrogator includes an oscillator which generates a first frequency signal, a counter which divides the first frequency into a series of lower frequency signals, at least one multiplexer having a series of input terminals selected ones of which may be grounded to provide an identification code, and an encoder connected to the oscillator, the counter, the at least multiplexer, and an antenna for selecting which of the signals from the oscillator, counter, and at least one multiplexer shall be supplied to the antenna.