This circuit was found in a Popular Electronics from the 90s. Its purpose is to disable the output of an FM or VHF receiver between stations, preventing the reproduction of hiss.
An interesting timer is shown in the figure, using one of the 4 NAND gates of the integrated 4001....
General Electric suggests this circuit in a 1980s documentation. The operational of the time is...
This simple adjustable source uses a PNP transistor that can be the BD136 for even slightly higher...