You can also uses the A gate for testing coaxial cable. You loop the pulse output thru the vertical input with a tee. Put a 100 ohm pot on the end of the line. Rock the pot back and forth and observe the waveform. You will see the reflected pulse go up and down, but when it flattens out, a match is achieved. Now remove the pot and measure the resistance which is equal to the impedance of the coax.
This method also shows also shows discontinuities such as splices and kinks that would create a reflection.
In the old days, TV engineers would use this method to "look" at the transmission line going up to the antenna, particularly after a nasty lightning hit.
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