This crystal oscillator is indicated for the calibration of IF steps of common radio receivers. The transistor admits equivalent as 2N2222 or BF494. The circuit is from an old American publication.
This full wave switch using SCR for the power grid is one of many versions we have on the site....
This is a basic astable circuit using the 555 IC and driving two LEDs. The phase on a rate giving...
This circuit was found in an American documentation from the 80's. The components are from that...