Power Supply Unit for the Swiss Enigma K
Enigma machines need electric energy to function. This energy is not needed for
the movement of the wheels, but only for the electrical circuit of the lamps.
It should therefore be considered a low-power device.
Most Enigma machines can be powered by an internal battery
(except the G31 models)
or by an external source, such as the battery of a vehicle, or a Power
Supply Unit (PSU).
The PSU shown here is very rare and was used with the
Enigma K machines
used by the Swiss Army and the Swiss Foreign Office. It can be connected
to a variety of mains voltages and has output terminals for 4 Enigma
The transformer is built into a small oak wood box, similar in design to
the box of the Enigma machine. It measures approx. 20 x 11 x 13.5 cm
and has a small leather strap on the top lid.
At the front, the lid is closed with an uncommon lock.
The transformer is hidden from view by a dark brown pertinax panel.
All connections are located on the dark brown pertinax panel.
At the top centre is a fixed rubber cable that connects the unit to the mains.
At the four corners are the connections for four individual Enigma machines.
Right in the middle is a power configuration plug that allows the unit to be
used on a variety of mains voltages.
The PSU is suitable for 110, 125, 145, 220 and 250 Volt.
The plug is entered into the required hole and then locked by screwing it in.
At the front of the panel are two fuses of 125 mA and 80 mA respectively.
The fuse holders accept 25 x 5 mm glass fuses.
Spare fuses are hidden in two holes in the wooden box, close to the hinges.
When not in use, the power cable is stowed away in the top lid of the wooden
box. Also in top lid is a single Enigma connection cable, with banana-type
plugs at one end and 'forks' at the other end, suitable for the screw-on
terminals of the Enigma.
The external power supply units were not part of the standard delivery from
the Enigma suppliers,
but were manufactured by the Swiss themselves.
This is also the reason why the lock on the front of the wooden box is
different to the locks of the Enigma box
and the Uhr box.
The Swiss Army ordered the external power supplies from
H. Stucki Tranformatorenbau in Bern (Switzerland).
On most of the surviving PSUs, a mains voltage of 220 Volt is selected.
If you want to use the PSU, it is advised to change the voltage to 250 Volt,
as the mains voltage in Europe has been increased to 230 Volt, or even higher
in some areas.
Selecting a higher voltage prevents the transformer from going into
saturation and grants the light bulbs a longer life.
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