This shield circuit is from a 1968s Motorola documentation. The relay is according to the supply voltage. R1 can be reduced to lower trigger voltages.
This small source was found in an English documentation from 1970. The diodes can be 1N4002 for...
-- We find this configuration very simple in a previous American publication of 1973. The...
This double T oscillator configuration can employ operational diamonds and the symmetrical supply...