<HTML><HEAD></HEAD> <BODY dir=ltr> <DIV dir=ltr> <DIV style="FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: 12pt"> <DIV>Here’s the response from my brother. </DIV> <DIV> </DIV> <DIV>*************</DIV> <DIV> </DIV> <DIV>Frequency standards for frequencies way above audio range were made of </DIV> <DIV>crystalline materials more than 60 years ago.  They certainly wouldn't be </DIV> <DIV>made of metal prongs.  The accuracy would be very low in that range.</DIV> <DIV> </DIV> <DIV>This device looks like it was for audio purposes, and since it is shaped </DIV> <DIV>like a tuning fork, it was probably used for a reference of some sort.  The </DIV> <DIV>coil is either there for picking up the vibration - like an electric guitar </DIV> <DIV>pickup - or for exciting the fork just enough to keep it humming.</DIV> <DIV> </DIV> <DIV>Tom</DIV> <DIV> </DIV> <DIV>***************</DIV> <DIV> </DIV> <DIV>Keeping it in oscillation is something I hadn’t considered.</DIV> <DIV> </DIV> <DIV>100 cps would be higher in frequency than AC hum. (60 cps)  G11 is quite low.  The tines are quite thin compared to what we use to tune pianos with.  It would take less energy to keep a thin tined fork in oscillation than a thicker tined fork.  The 3 VDC power supplied would be to activate the coil as opposed to sensing the coil as in a guitar pick up which typically is a much lower voltage.  A vibrating tine crossing through the magnetic flux would generate a voltage that would then act as a pick up.  I’m going to put my vote on a small voltage to keep the tines moving.  The extra hardware at the ends of the tines has me puzzled.</DIV> <DIV> </DIV> <DIV>That was fun.</DIV> <DIV> </DIV> <DIV>Lar</DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV></DIV></DIV></BODY></HTML>