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Hagelin HC-520 CRYPTOMATIC
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Pocket electronic cipher machine
The HC-520 was a portable electronic cipher machine developed by
Hagelin (now: Crypto AG) in Switzerland.
It was introduced in 1977 as part of the HC-5xx CRYPTOMATIC family
of machines that succeeded the H-4605.
The HC-520 and was one of the first fully electronic cipher machines.
It resembled a calculator and was small enough to fit inside the pocket
of a coat.
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The HC-520 looks like an electronic calculator and was considered
very compact at the time.
It is based around a PDP-8 compatible Intersil IM6100 processor
and is powered by a built-in rechargable 6V battery pack.
It has a very reliable keyboard with rubber key-tops and produces
its output on a custom LCD screen.
It came in two variants: a military version,
in a green case, and a civil version in a white (cream) case.
Apart from the colour of the case, the machines are identical
and both versions are known to have been used by the military.
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The HC-520 is extremely easy to operate and came with a plastic instruction
card with a flow-chart on either side; one for ciphering and one for
deciphering. Both sides can be downloaded below.
The machine shown in the pictures is an early prototype with
serial number 43.
Judging from the date stamps on the ICs inside the machine, it was
developed around 1977 (see below).
According to Crypto AG it was sold until 1987.
The HC-520 wasn't cheap; in 1977 it had a price tag of 5000 Swiss
Francs (approx. 3250 Euros).
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The HC-520 is part of the CRYPTOMATIC family of machines and is compatible
with the following family members:
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- HC-520 (Pocket version, resembling a calculator)
- HC-530 (Suitcase version)
- HC-550 (Desktop model, based on Siemens T-1000)
- HC-570 (Desktop model)
- HC-580 (Desktop model, based on Siemens T-1000)
- HC-590
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The HC-520 contained a (DEC) PDP-8 compatible microprocessor, complete with memory,
ROM and various electronic circuits. Nevertheless, it is a very compact
machine, which is very unique considering its age.
The entire machine consists of a sandwich of three PCBs (Printed Circuit
Boards). The one on top of the stack is the keyboard with very robust
dome switches.
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At the bottom is the processor board with the IM6100, the memory and the
backup battery. The middle board contains the display and the rest of the
electronics, and is by far the most complex one.
It is clearly visible that the middle board consists of two epoxy PCBs (rigid)
with a flexible PCB in between them. This is called a flex-rigid design.
The flex part is extended at the left and folded directly into the LCD display.
A very unique design feature for the era, which is still in use today.
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Just visible in the above image, is the tamper-switch that is fitted to the
bottom board. It has a small metal arm that is operated by the only screw that
holds the case together. When this screw (located inside the battery compartment)
is removed, the entire memory of the HC-520 is wiped, complete with the
current key
and the message.
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The image on the right shows the two main PCBs of the HC-520. The leftmost
one is the processor board with the large 40-pin processor at the centre.
The RAM-memory is located at the top left (the 6 ICs with the golden caps)
and the software is stored in three adjacent ROMs just below the processor.
The processor board connects to the display board (right) with a single-row
header. Two I/O expanders (the white chips at the bottom left) are used to
connect the processor to the rest of the electronics.
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Looking at the date stamps on the various chips, the machine was built
around 1977. Particularly important in this respect, is the date stamp
on the masked ROM chips (i.e. the chips holding the software). These
are custom-built and have to be ordered in large quantities.
It is therefore safe to assume that the HC-520 was introduced in 1977.
Click any of the images on this page to enlarge.
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The HC-520 needs two batteries to operate correctly. One is the backup
battery which will be described later. The other one is the battery
pack that is fitted just above the display.
Main batteries
Most HC-520 machines were supplied with a rechargeable battery pack
consisting of 5 penlight (AA-size) NiCd cells of 1.2V each. This
produces a total voltage of 6V. Please note that NiCd cells will
gradually degrade over the years so, if you have a working HC-520,
you may need to replace the cells. Furthermore, NiCd cells have the
tendency to leak if they are not used, which can be potentially
hazardous for the interior of the machine.
If you want to use the HC-520 with rechargeable cells, a suitable
battery charger should be used. It can be connected to the 9-way
D-type connector at the rear of the unit.
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The HC-520 can also be used without the batteries. In that case,
a suitable PSU (Power Supply Unit) of 6V should be connected to
the D-type connector. Only two pins of this connector are used:
- Pin 1: (positive terminal, +6V)
- Pin 5: (negative terminal, 0V)
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When connecting a power supply, use the above drawing as a guide.
It shows the 9-way D-type connector when looking into the socket
of the HC-520.
Backup battery
The backup battery is a potential cause of problems.
It is a small black unit with 3 Lithium cells inside it.
Due to the age of the HC-520, these batteries will be exhausted
by now. Like all empty batteries, they may start leaking and could
cause permanent damage to the processor board.
It is therefore highly recommended to remove this battery as
soon as possible. The HC-520 can operate perfectly well without
it. The only purpose of the backup battery is to maintain
the message key (and the message) whenever the main battery
is flat or being replaced.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 15 January 2011 - 15:15 CET
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