Transmitter/responder systems

Claim 1

A responder comprising: (a) receiver means for receiving a transmitted signal S1 comprising a frequency f1; (b) generator means for generating a carrier frequency f2 of a carrier component of a transmittable signal S2 comprising carrier frequency f2 and code; (c) logic means for enabling frequency f2 to be in mathematical relationship wherein f1 is related to f2 by a function of at least one variable having a value other than zero and one with signal S1, said logic means comprising; (i) at least one memory means, adapted to be programmed for storing code, (ii) at least one modulation means for modulating said carrier component of signal S2, the modulation being under control of at least a portion of said stored code, such that said frequency F2, will be encoded to provide said mathematical relationship with said frequency f1 and, (iii) at least one clock means for providing at least one clocking signal for controlling access of at least a portion of said stored code to said at least one modulation means; and wherein means are provided whereby said at least one memory means is adapted to be programmed with said code by receiving at least one programming signal to be provided by an electromagnetic linkage between said responder and at least one source of said at least one programming signal, said at least one programming signal comprising code to be routed to said at least one memory means so as to provide said stored code.