This simple circuit, found in American documentation, uses only one relay that locks when any of the sensors is activated. To reset, simply turn off the power for a moment.
We found this circuit in the Linear Applications Handbook of the 1994 National Semiconductor. The...
This circuit from a Japanese publication in 1968 uses germanium transistors from the time like the...
This circuit, found in a 1994 publication, allows the use of two common analog telephone sets on a...