WEN H. KO 
1141 
Table IV. — Performance of PFM Telemetry Trans- 
mitter 
EF frequency 115 MHz 
Signal bandwidth necessary for the 
receiver (I.F. stages) — 1 MHz 
Signal frequency band 0.4 500 Hz 
Period for zero input signal — 220 /tsec 
Modulation sensitivity 120 /tsec/mV of input 
Maximum input signal ±1 mV 
Power consumption 100 /tW at 2.6 volts 
tioii,2i-25 it is possible that it can be used to by- 
pass sensory organs to generate hearing or some 
degree of vision directly at the central nervous 
system level as well as to temporarily alter per- 
sonality or induce sleep. 
The stimulating circuit is generally a simple 
radio-powered passive resonant circuit. Batter- 
ies, rechargeable batteries, radio power, and 
energy converters have been used to power these 
implant stimulators. An implant stimulator 
with feedback information is shown in Figure 
5. The stimulating parameters for heart, blad- 
der, nerves and muscles are summarized in 
Table V. 
The major problems in stimulators are power 
supply, packaging, electrodes and tissue dam- 
age. The first two problems will be discussed 
later. Requirements for electrodes include: 
Table V. — Stimulating Parameters 
Heart 
Bladder 
Pulse width (msec) 0.1—10 0.1—10 
Pulse Rate- _ 30 — 200 ppm 15 — 35 pps 
Pulse voltage (volt) 0—9 10 
Pulse Current (mA) 4 — 45 50 
Nerve 
Indirect Muscle (Via Nerve) 
0.05—1 
5—100 pps 
0—10 
0.1—10 
Intramuscular 
0.1—10 
1 — 50 pps 
0—10 
0.5—10 
Surface 
0.1—10 
1 — 50 pps 
10—60 
5—50 
BODY OF SUBJECT 
EXTERNAL 
CON TROL 
o » 
TRANSMITTER 
MONITORING 
RECEIVER 
FiGtJRB 5. — Block diagram of implant stimulator circuit. 
i 
