[Monkey Wrench]

in the abscence of a scope, You could likely just feed the signal into the input of a radio, like for example if you have a cheap portable radio that you dont care too much about with a microphone input or "line in" a phono imput will do. those are usually pretty sensitive inputs.

you can protect that input with a 1 meg resistor, it will allow the signal through , just not lots of amperage. instead of the pulse being represented as a wave form trace on a scope, you'd hear a buzz or a whine being amplified through the radio. if frequency changes you can hear the tone change. - this is basically a "poor man's oscilloscope".

you probably just need the one wire. I'm sure most here have tried connecting things to an amp and noted that even just touching those inputs with your hand will produce noises, because they are very sensitive.

if you want to couple things like that without an electrical connection placing a few loops of input near a few separate loops leading to the amp will provide coupling, its called a loose coupler or loose coupling.. lets say 10 turns around a toilet paper tube and another ten near to them, like that..

Then there is no actual electrical connection other than what is being passed though the air by way of induction. all you are creating is basically a transformer that has no electrical connection between its input and output and that can be used to protect your circuits from each other. the potential across such a transformer is limited, you can't create a hot or ground path between the two. its just a way to protect both circuits from each other by keeping them physically insulated from one another.