This circuit is used in VHF and UHF superheterodyne receivers. The circuit is from the 1964 RCA transistors manual. Equivalent transistors such as the BF495 can be used.
This alarm circuit with sensors in series was found in the Electronics Now magazine of June 1994....
An advanced motor control software plug-in for Microchip’s MPLAB® X Integrated Development...
This General Electric circuit triggers on after 60 seconds. The circuit is from 1967 but can be...