A method of communicating data between a remote device and an inductive power supply using keyed modulation, said method comprising: receiving inductive power via a variable frequency power transmission signal from the inductive power supply; encoding a data stream of bits into a communication signal; and generating a modulation signal based on the communication signal and a modulation clock signal, wherein each bit of the data stream is represented by a plurality of modulations in the modulation signal; modulating the variable frequency power transmission signal according to the modulation signal by toggling a load of a communication transmitter; and varying the modulation clock signal based on variations in a frequency of the variable frequency power transmission signal, wherein the variable frequency power transmission signal is capable of varying in response to a change in at least one operating parameter of the inductive power supply, whereby the modulation clock signal is varied based on the change in the at least one operating parameter of the inductive power supply, wherein the modulation clock signal is phase locked at a harmonic frequency of the variable frequency power transmission signal, characterized in that said modulating includes: producing a first modulation control signal formed by exclusive OR-ing (a) the modulation clock signal operating at the harmonic frequency and (b) the communication signal; producing a second modulation control signal formed by inverting the exclusive OR of (a) the modulation clock signal operating at the harmonic frequency and (b) the communication signal; toggling the load according to the first modulation control signal during a positive half of the variable frequency power transmission signal; and toggling the load according to the second modulation control signal during a negative half of the variable frequency power transmission signal. receiving inductive power via a variable frequency power transmission signal from the inductive power supply; encoding a data stream of bits into a communication signal; and generating a modulation signal based on the communication signal and a modulation clock signal, wherein each bit of the data stream is represented by a plurality of modulations in the modulation signal; modulating the variable frequency power transmission signal according to the modulation signal by toggling a load of a communication transmitter; and varying the modulation clock signal based on variations in a frequency of the variable frequency power transmission signal, wherein the variable frequency power transmission signal is capable of varying in response to a change in at least one operating parameter of the inductive power supply, whereby the modulation clock signal is varied based on the change in the at least one operating parameter of the inductive power supply, wherein the modulation clock signal is phase locked at a harmonic frequency of the variable frequency power transmission signal, producing a first modulation control signal formed by exclusive OR-ing (a) the modulation clock signal operating at the harmonic frequency and (b) the communication signal; producing a second modulation control signal formed by inverting the exclusive OR of (a) the modulation clock signal operating at the harmonic frequency and (b) the communication signal; toggling the load according to the first modulation control signal during a positive half of the variable frequency power transmission signal; and toggling the load according to the second modulation control signal during a negative half of the variable frequency power transmission signal.