The J-43 has a large toggle switch on top of the base on
the right side. The toggle switch is marked "OPEN" at the back
and "CLOSED" at the front".
(click to enlarge)
(click to enlarge)
Here you see the additional binding
post, marked "RELAY", and the small metal wicket mounted on the
right rear of the base. You can also see the words "GND." and "KEY"
stamped in white near the binding posts on the frame.
On the bottom of the frame you can see the filled grooves that
connect the toggle switch to the RELAY binding post and the
anvil of the key. The toggle switch has no effect on the
normal operation of the key,
but when the switch is set to CLOSED there is continuity between
the "GND." (left) binding post on the frame and the "RELAY" binding
post on the right rear of the base.
(click to enlarge)
(click to enlarge)
This rare variation of the J-43 has a very complicated plunger and release
switch which replaces the usual simple toggle switch. I have no idea what the
three little red dots might be, or if they are even official parts of the key, since
this is the only one I have ever seen.