Oscilloscope

First, try to confirm the timing by oscilloscope.

In nineteen fifty-eight, a scientist at the Brookhaven National Laboratory in New York State developed a game he called "Tennis for Two." William Higinbotham played it on a scientific device called an oscilloscope. The scientist did not see that such a game could become widely popular. But others did.

Next, try to confirm the deviation with an oscilloscope.

If two waveforms have no phase no phase or frequency relationship, there is seldom reason to observe both waveforms simultaneously. However, these oscilloscopes do permit the simultaneous viewing of two such unrelated waveforms, using alternate triggering. […] If the fuse blows, the “ON” indicator will not light and the oscilloscope will not operate.