As pacemaker check system via telephone, we started the experiment in September 1973, considering acoustic coupling transmission and direct wired coupling receiving.
Making sure of its effectiveness, we went to business in October 1974.
Acoustic coupling transmission has two methods, two channel (ECG, PMP) and one channel (ECG).
Output of tansmitter is limited below 0.9Nm2/wave, therefore two channel method it must be 0.4Nm2/wave.
Sixty% of patient cases, is impossible to transmit by two channel method.
In one channel method (0.9Nm2/wave), one case of 60 cases was impossible, all of others possible.
