The transistor can be a BC548 and the coil has the following characteristics for 1 MHz. L1 has 80 turns of wire 28 in a ferrite rod and L2 of 30 and 40 turns.
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....