1140 
MONITORING 
w 
Clamping 
Receiver Circuit 
Frequency 
to voltage 
Converter Filter 
Ampl ifier 
- + 
JUlTLJtftft 7^ 
OUT 
B. RECEIVER 
Figure 4. — Block diagram of single channel PFM transmitter. 
examined together with the phase locked loop 
for pulsed signal to improve the system per- 
formance. 
IMPLANT STIMULATION 
Electrical stimulation of the nervous system 
for remote control of animals v^^as tried as early 
as 1934.20 However, its widespread research 
and clinical application is relatively recent. The 
heart pacemaker is the best known clinical de- 
vice. In addition to the heart, stimulation has 
been applied to the bladder for voiding; the 
phrenic nerve for diaphragmatic contraction; 
baroreceptors for reduction of blood pressure; 
the spinal cord for pain suppression; and par- 
alyzed muscle for regaining motor functions. 
With recent developments in brain stimula- 
