Abstract: A receiver for receiving and demodulating FSK modulated data signals has improved sensitivity over substantial frequency offsets between the transmitter and receiver local oscillator, and low spurious electromagnetic radiation. A quadrature coupler splits the received signal into in-phase and quadrature phase signals which are then mixed down to baseband, filtered, and limited. An RC circuit at the output of a four flip flop demodulator averages the flip flop output signals. A voltage comparator outputs a logical 1 if the voltage at the output of the RC averaging circuit is greater than one-half the supply voltage; otherwise the comparator outputs a logical zero.