Multichannel recording of cardiac potentials

An inexpensive system for the simultaneous recording of 256 cardiac electrograms is described. Time division multiplexing of cardiac potentials by digital circuitry provides a single video signal which is recorded on video tape. During playback a demultiplexer reassembles the separate signals. Measured channel characteristics demonstrate a bandwidth of 170 Hz, a noise level of 0·2 mV peak-to-peak, and a crosstalk of −27·5 dB. The design has flexibility in that individual channel bandwidth can be exchanged with the total number of channels according to the dictates of signal requirements. To illustrate this flexibility a second system is described which provides 64 channels whose measured characteristics include an 880 Hz bandwidth, a noise level of 0·14 mV peak-to-peak and a crosstalk of −33 dB.