This circuit was obtained in a documentation from the National Bureau of Standards of 1968. The circuit is of low current and the output can be changed to voltages between 2 and 30 V.
This circuit was found in a 1987 magazine. It measures monitors the heartbeat through a...
This crystal-controlled circuit was obtained from a 1980s documentation. The power supply should be 5...
This circuit is from 1957 Raytheon documentation. The phone must be high impedance with 600 ohms...