Never understood the tracers, other than a contact, bio or other, asked to listen to a contract, what do you hear. Me gurgling noise like water down a plug, operator, no that's a 4 blade, 3 shaft bla bla. Like SB they broke them I fixed them, that's why I said user maintainer wouldn't work.I fixed it when the users broke it - never did understand all the wiggly lines. Also, in those days, it was black and white, as in burnt paper trace or green lines on a CRT. None of this coloured malarkey!
And no - it doesn't go 'beep' on the display every time a full rotation is seen, same as RADAR!