This circuit was found in an English documentation from the 90s. It uses a PLL CMOS 4046 and is powered by a 9 V battery. The sensors are two electrodes that must be held by the person.
This circuit from March 1984 Radio Electronics is intended to allow the use of an oscilloscope to measure...
The circuit in the figure uses the four current amplifiers of the LM3900 to generate a sawtooth signal...
This amplifier was found in a technical documentation from the 1970s. The circuit uses 2N2218...