PC resistance meter (CB20544E)

We found this circuit in English documentation for PCs from 1996. The ZN448 is a very uncommon integrated circuit today. It is an interface circuit.

Digital to Analog Converter (CB397)
This circuit source a voltage proportional to the number of the input pulses. The circuit has a...
Sine to Square Converter (CB4824E)
This circuit is from a 90's Radio Electronics. The circuit operates accurately up to about 15 kHz...
Battery Step Up Switched Regulator (CB6065E)
This is a circuit suggested by Linear Technology in a 1980s documentation. The integrated circuit is from...