FORD crank pickup

[Tom Cloud]

Looked at the crank pickup output this weekend on my '82 Bronco.
(I'm not using it anymore.)  The pickup was unloaded -- except
by the 10X (10-megohm) 'scope probe.

The signal was a negative going sawtooth of about 2 to 3 volts pk
(checked idle speed only) and the sharp edge of the sawtooth on
the rise to zero.  Sorry, don't remember the pulse width.

My question is ....

  - why does the pulse not ring positive ??  Is there a diode built
into the pickup -- and, if so, it must be copper oxide or such as it'd
have to be very low VF.

The connector has two wires, which I assume to be a coil (haven't
done a resistance check) and a third quick disconnect type which
I assume to be a shield ??

Anyone know about this crank sensor ?

thanks,
Tom Cloud