Well, it was a Good Idea for the Time....
This article outlined a scheme to measure and standardize the 'Pull In' time of a large number of cart machines. It was published in'Broadcast Management and Engineering' in October, 1984....
A pulse from the 'Cart Start' circuitry was also used to trigger the sweep on a scope.
A tone recorded on the cue track traced out the reaction
time of the solenoid.