Photocardiograph (CB21738E)

We found this circuit in a 1969 Popular Electronics. It measures the heartbeat by changing the transparency of the finger.

ATtiny1617 8-bit AVR Microcontrollers
August 2017 - Microchip's new ATtiny1617 8-bit AVR microcontrollers running at 20 MHz and 16 kB...
Active Bandpass Filter (CB6723E)
Found in a 1970 American publication, this circuit uses transistors of the time. These transistors...
APS1 Series of Optical Couplers
May 2017 - Panasonic's new APS1 series of optical couplers with 3 750 V insulation and up to 50...