Some while ago someone on PICList described chest band type pulse
measurement systems.

These detect signals from the heart and send a short pulse to a coil which
is picked up by a coil in the adjacent receiver. Probably near field and I'm
not sure that the circuit at either end is resonated to a specific
frequency.

I would be interested to know if anyone has practical experience of these
systems. I am interested in slightly extending the range of one such system
to make it more robust in the presence of metal shielding and
electromagnetic interference. As far as I've delved so far the transmitter
uses a single 4069 and the receiver seems to use 2 x 324 (although the
application would hardly seem to need so many devices).
All sorts of possible approaches suggest themselves but knowing what others
may have done in this area would be interesting.

Also - who was the original person who seemed reasonably aware of these
systems.

      Russell McMahon

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