This circuit is from a Ferranti publication of 1968. The circuit generates a signal according to the crystal. The transistor may be a modern equivalent.
May 2016 - It can be obtained from Mouser Electronics new microcontrollers from Texas MSP430...
March 2017 - Coilcraft SLR series inductors for currents up to 100 A can be obtained from Mouser...
This circuit eliminates hiss and other noise from audio sources by cutting frequencies above 10...