Delete comment from: Ken Shirriff's blog

DHess said...

The diode increases the noise immunity by raising the high logic level voltage. The use of a diode that way is common in both integrated and discrete bipolar level shifters including ICs designed immediately after that era.

A good example of logic threshold shifting using diodes can be found in the ubiquitous MC1488 line driver used for RS-232 applications.

Jun 22, 2021, 9:42:44 AM

Posted to Inside a transistorized shift register box, built in 1965 for Apollo testing