[GreenKeys] Distortion problems

[Jim Haynes]

You probably don't need 120V for contacts, although it doesn't hurt.
See Western Union Technical Review 5:1 January 1951 p. 32 and 15:4
October 1961 p. 149.

Model 28s also expect enough voltage to break through the oil film,
even though they are inside a box marked "do not oil".  Model 35s
I believe had the same contacts but gold plated to operate at low
voltages; and if operated at high voltages the gold would be vaporized
off.