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Tesla PS-31 / PR-31 (Stasi)
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Portable surveillance radio
The PS-31 was a rather large semi-portable radio station with voice
scrambling, developed and manufactured by Tesla in Czechoslovakia.
It consists of various components, including the actual PR-31 transceiver.
The radio was introduced in the early 1980s and was intended for
police surveillance, covert operations, observation tasks
and secure communication.
As it was also used by the secret service of the former DDR, the Stasi,
it is often called the Secure Stasi Radio.
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The PR-31 is a simplex radio that operates in phone (voice) in the
80MHz band. It has provisions for 70 pre-determined channels.
Each user is issued a special code-key that is used for identification.
At the start of each transmission, the ID is transmitted to the master
station.
The radio is normally used inside the protective leather case that can
be fitted to a belt, or carried on the shoulder, using the provided
strap. When not in use, the handset can be slotted onto the shoulder strap.
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A separate handset contains a combined microphone/speaker and connects to
the radio by means of a special 7-way screw-on plug.
On top of the handset is a rather 'heavy' push-to-talk switch (PTT).
At the front of the handset is a red EMERGENCY button and a red LED.
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The PR-31 allows a secret identification number to be inserted at the start
of each transmission. This way, the master station can varify the identity
of the person at the other end. This is particularly useful in situations
where agents were working in shifts and had to hand the radio over to the
next person on watch.
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The operator has to insert his key into a socket on the front panel of the
radio. It has a special rig to ensure that it is always inserted the
correct way around. They key itself has two rows of metal notches which
together make up the unique ID.
After inserting the key, the user has to activate it by turning it
1/4 clockwise, so that it lines up with the '1' mark. The key has to
be left in place for the duration of the session.
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The PR-31 has a 7-pin connector at is front panel. The connector is used for
connection of a handset, such as the one shown here. This handset is supplied
with the radio as a standard accessory. It is used both as a speaker and a
microphone and the PTT switch (push-to-talk) is mounted on the top.
At the front panel is a large red button and a red LED. The red button can be
pressed in case of an emergency. The radio then transmit the distress code.
When not in use, the handset can be clipped to the shoulder strap.
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The PR-31 is supplied with two different antennas: a long rather stiff antenna
and a small flexible helical antenna. The long one gives the best operating
range, whereas the helical is used for convenience.
The image on the right shows the helical antenna being inserted in its socket.
A screw-on terminal is used, similar to TNC.
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The PR-31 is powered by 12V battery pack that is inserted into a slot at the
bottom of the radio. Normally, two battery packs were supplied with the unit,
so that one could be charged externally, whilst the other one is used.
It is also possible to recharge the battery whilst it is seated in the radio,
by using two contacts at the bottom.
The battery contains 10 1.2V NiCd cells with a capacity of 500mAh.
It is quite likely that the batteries of the surviving radios have died
and can no longer be recharged.
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If you want to bring an old radio back to live,
it might be a good idea to replace the batteries with NiMH cells.
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The complete PS-31 radio station, consists of the following components:
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- Radio PR-31
- Handset PO-31
- Helical antenna PA-31
- Fixed antenna PA-32
- Battery 12V (10 rechargeable NiCd cells)
- Leather carrying case
- Code-key
- Documentation
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Sunday, 04 May 2014 - 22:52 CET
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