This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
The power supply shown can supply voltages of approximately 0 V to 12 V with a maximum current of 4.5 A,...
This indicator was found in a 1974 publication, but it can be fitted with the BC548 transistor or...
Used with infrared remotes at the time, this circuit was found in a 1991 RE Experimenter Handbook....