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The Junker DBGM Key
Hirschmann Plug Details
|Many of the Junker keys have a cable terminated in a Hirschmann plug,
as shown above. These plugs were standard on many 3-wire connections
in Europe for decades. In the older configuration, the center terminal
would be ground, and the outer two for the front and rear contacts on
the key. Germany militery applications did not require the rear
contacts after around 1955 and so these plugs follow a different
pattern, as detailed below. Hirshmann is said to have been the
inventor of the ever-popular "banana plug" and the "aligator clip."
If you have the Hirshchmann plug you have a few options for connecting the key to your more modern equipment:
Replace the cable and plug
Wire a new plug onto the existing cable
Solder connecting wires onto the pins of the Hirschmann plug.
You can easily deduce the connection pattern with a multimeter, and you should certainly verify it before connecting to live equipment, but here is the pattern
we have seen consistently with the current batch of Junker keys:
With the plug held as shown, with the screw on the top, you should find continuity as follows:
Pin A on the plug is wired to terminal 2 on the key (common or ground)
Pin B on the plug is wired to terminal 3 on the key (rear contact, probably not connected internally)
Pin C on the plug is wired to terminal 1 on the key (front contact).
So for ordinary operation as a straight key you will want to use terminals 1 and 2 on the key (A and C on the plug).