Without giving too much away............ (yuk yuk yuk)

One can always post your questions at:
http://www.vibinst.org/default.htm

and usually somebody will be happy to answer.

Phase indicators can be a variety of schemes or devices. Proximity
probes, and notch. Strobe light. Magnetic interrupter. Photocell.
Even the old proverbial pencil and masking tape!

Kent Felkins
Tulsa