This circuit generates frequencies determined by R3 and C1. We found it in the Radio Electronics magazine of May 1988. The power supply must be symmetrical.
This is the basic configuration of a monostable TTL with the 74121. The trip is done with an NC...
This fixed source configuration with 78xx series regulators has already been explored in several...
In the figure we have a TTL logic interfacing circuit as CMOS logic using a 6N139 optocoupler...