Abstract: Apparatus is disclosed for sensing and transmitting the stimulating pulse of an implanted pacemaker over readily available, low-bandwidth transmission media to a remote receiver capable of measuring the pulse width to provide an indication of the condition of the pacemaker energy source, e.g. a battery. In particular, the sensing and transmitting apparatus detects the electrical activity, e.g. the EKG, of a patient through attached electrodes and modulates a carrier or tone of a suitable frequency to be transmitted over the low-bandwidth transmission medium to the receiver, along with a pulse signal multiplied by a selected, fixed factor dependent upon the carrier frequency of the signal and the other information to be transmitted to the receiver.