One of my friends is an electronic technician amateur in repairing of television or radio receivers. He said he is made a signal injector circuit to detect the signal in various sectors.
For example: in the sector amplifier, when the input signal of this circuit, if the amplifier is good, we can hear the sound from the speakers. Or we can check signal the following points by the oscilloscope more easily. Or we will apply to check the vertical yoke driver of the TV, too.
When see in circuit as shown figure this below, he used two transistors join together to be astable multivibrator which have signal output frequency of 1,000Hz in square wave form.
this circuit used only the power supply of 1v to 5V so he has only battery aaa 1.5V, doing level amplitude voltage peak output lower than 1vp be safe for the circuit is tested by this tool.
The creation of this circuit is simply only composted all parts in the perforated board.