A power supply detection circuit biased by at least two power supply voltages for controlling a signal driver circuit. Upstream and downstream amplifiers, powered by upstream and downstream power supply voltages, respectively, process an original control signal to produce a differential signal via output signal electrodes. Capacitances coupling respective ones of the output signal electrodes to the downstream power supply voltage and the circuit reference potential discharge and charge respective ones of the output signal electrodes in relation to initial receptions of the upstream and downstream power supply voltages and original control signal, following which voltage clamp circuitry maintains such discharged and charged states pending reception of the original control signal in a predetermined state.