An ingestible apparatus produces and processes physiological signals representative of a physiological parameter. The apparatus measures the physiological parameter from within the body of a living entity. The apparatus includes a physiological transducer circuit to sense the physiological signals, a processor to process the physiological signals in response to the physiological transducer circuit, and a transmitter that transmits the processed signals during transmission intervals which are alternated with idle intervals. The apparatus further includes a capacitor-based circuit, including at least one capacitor, to accumulate sufficient charge during one of the idle intervals to supply power to the transmitter during one of the transmission intervals.