We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
When this alarm is off current drained is very low, only about 60 µA. The circuit can be powered...
This circuit, from the 1990 Motorola Dataar Databook, can be implemented with other comparators. The...
The integrated circuit in this application is from the 80's, not being common nowadays. It...