This Schmitt trigger was found in old documentation. The transistors can be of the general-purpose type like BC548 or even 2N2222.
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...
The basic integrated circuits of this 1988 multimeter are no longer very common today, but if...
This circuit is from an old publication of the 70's. It can be implemented with modern transistors like the...