I looked at the data sheet of the sel-2407 and interestingly it states "demodulated" IRIG-B, which seems a bit odd. Either it's a modulated code i.e. a sinusoidal wave with amplitude modulation (usually about 3:1), or it's what we call a DC code i.e pulse width data stream not superimposed on the 1 KHz carrier. Rob Kimberley