Suggested by General Electric in a 1965 document, this circuit can accept a greater number of sensors. When anyone opens the SCR it fires powering the load.
We found this circuit in a 90's Radio Electronics. The low power circuit activates a 12 V relay...
This general-purpose two-transistor circuit was found in the November 1993 issue of Electronics Now. The...
We found this circuit in an American 1980s documentation. The operational ones used are not common...