Miniature ingestible telemeter devices to measure deep-body temperature

A miniature, ingestible telemeter device for transmitting information relating to deep-body temperature of a subject comprising:

• a free-running multivibrator having complementary transistors;
• an r-f oscillator having a predetermined resonant frequency, said oscillator including an inductor for radiating r-f energy;
• a buffer amplifier coupled between said multivibrator and said oscillator;
• a battery connected to said multivibrator, said buffer amplifier, and said oscillator;
• said free-running multivibrator having temperature-sensitive circuit means for turning on and off said multivibrator and controlling its output pulse frequency when in the on state, said temperature-sensitive circuit means comprising an R-C circuit, said R-C circuit being connected to said battery and to both of said complementary transistors, said R-C circuit including a thermistor;
• means in said multivibrator for turning on said buffer amplifier when said complementary transistors are conducting;
• means in said buffer amplifier for turning on said oscillator when said buffer amplifier is on;
• said multivibrator, said buffer amplifier and said r-f oscillator being in an off state and drawing an insignificant current from said battery when said thermistor is subjected to or below a predetermined temperature which is below the deep-body temperature of the subject ingesting said telemeter device, said free-running multivibrator, said buffer amplifier, and said r-f oscillator being in an on state whenever said thermistor is exposed to a temperature above said predetermined temperature, the output frequency of said multivibrator being proportional to the temperature of said thermistor, said oscillator generating bursts of r-f energy at the output frequency of said multivibrator, the period between successive bursts being inversely proportional to the temperature of said thermistor.