This SCR timer was found in an old English documentation. The SCR can be the TUIC106 and modern equivalent transistors like the BC557 for TR1 and BC547 for the others.
The transistors are 2N918, 2N3464 and other RF equivalents of the time for Q1. For Q2, 2N3399, 2N2894...
This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit...
This interesting intercom circuit was obtained from an Argentine publication from the 1970s....