Spy sets
Burst encoders
Logo (click for homepage)
USSR spy radio base station
The R-355 is a controller for a spy radio base station, developed in the USSR in the 1960s. It was designed to be used on radio networks that consisted of a plethora of Russian spy radio sets, including the the R-353 and the R-354, and was able to record burst transmissions. Initially, the messages were recorded onto a magnetic disc, but later tape recorders were used as well.
During the Cold War, most countries of the Warsaw Pact (i.e. Eastern Europe and the USSR) ran large espionage networks in Western Europe and elsewhere. Spies and agents operating on foreign territory, often used spy radio sets to stay in contact with their homeland and report any information that had been discovered.

In order to minimise the risk of detection and interception, they often used burst transmitters in order to keep their transmissions as short as possible. Keeping the transmissions short, would defeat any direction finding effort by the enemy.
R-355 spy radio base station controller

A burst encoder allows a pre-recorded message to be played back at very high speed, so that the transmitter is only briefly on the air. At the remote end, a fully automated reception station would pick up the burst transmission and record it on a disc recorder, so that it could be played back later at a lower speed. The R-355 is the central control unit at the heart of a reception station.

It is currently unknown how many R-355 units were built, but given the fact that they were used in all countries of the Warsaw Pact and that multiple units were needed in a single reception station, it seems reasonable to assume that several hundreds were produced in the USSR.
R-355 spy radio base station controller R-355 spy radio base station controller Indicator lights and function buttons Carrying grip (left and right side) Mains socket at the rear Cable for connection of a tape recorder to the R-355 Technical manuals R-355 interior

All controls of the R-355 are located at the front panel of the device. At the left is the built-in oscilloscope, consisting of a cathode ray tube (CRT) and four adjustment knobs. Above the CRT are four calibration adjustments. At the right is the Power Supply Unit (PSU) that is suitable for connection to the 127 or 220 V AC mains (selectable with a toggle switch hidden behind a white lamp cap at the right). A meter with a rotary selector allows the various internal voltages to be checked. The meter is also used for checking the recording level (by setting the selector to МАГ.).

The various controls and adjustments for frequency searching, recording speed, IP filter selection and audio volume are located at the center part of the front panel, with the MODE selector at the left (to the right of the CRT). At the bottom is a small recessed panel with five push buttons and five control lamps. These buttons allow direct control over the various functions of the R-355.
Mode of operation
The mode of operation of the R-355 is selected with a 5-position rotary switch to the right of the CRT, marked ВИД РАБОТЫ (MODE). This selector offers the following settings:
  1. АВТ. ОТКЛ. - Auto OFF
  2. ПО РАСПИС - Stand by
  3. ПО КОНТРОЛЮ - Operation
  4. ПРОВЕР. АВТ. РАБОТАЕТ - Check auto (use push button for checking auto-start)
  5. НЕ РАБ. - No mode (passive)
Furthermore, the operation of the R-355 is controlled by five push-buttons that are located in a recessed area at the bottom center of the control panel. Above each push button is an indicator light that shows which function is currently selected. The following functions are available:
  1. ПРИЕМ - Reception (RX)
  2. ПЕРЕДАЧА - Transmission (TX)
  3. ПОДГОТ. ЗАПИСИ - Recording (REC)
  4. ВКЛ. - ON
  5. ОТКЛ. - OFF
The rightmost two indicator lamps have the following meaning:
  1. ОТВЕТ СИГНАЛ - Response signal
  2. МАГ. - Megnetic Disc or Tape Recorder
R-355 seen from the front Indicator lights and function buttons AFC switch, headphones socket with volume control, and morse key socket Scanning control and recording speed adjustment Meter and meter-selector Close-up of the two fuse holders IF filter selector Close-up of the oscilloscope section Peripheral sockets at the right corner
From left to right: the power light, the power switch and the 127/220 V voltage selector (behind cap) Frequency scanner start/stop Timebase adjustment (coarse) Recording speed adjustment Oscilloscope calibration Oscilloscope calibration Close-up of the Cathode Ray Tube (CRT) MODE selector with check button

System description
A burst transmitter is a device that allows a message, usually encrypted as a long sequence of seemingly random numbers, to be pre-recorded. This was generally done on a magnetic tape, or on photo-film by punching a series of holes. Once the message was complete, the spy radio set was used to contact the home office and, once a connection was established, replay the message at very high speed by means of radio telegraphy (morse code, or CW) as a series of tones (burst).
Because the message was played back at very high speed, the transmission would only take a couple of seconds, which was insufficient for effective direction finding by an interceptor.

At the remote end (i.e. home office), a series of fully automated recording stations were awaiting any burst transmissions at a scheduled set of frequencies on the shortwave bands. Such a recording station generally consisted of a short­wave receiver, a controller and a magnetic disc recorder. The R-355 was a typical controller that was used at the heart of the recording station.
Phones and morse key sockets. At the right the black socket for the tape recorder.

It is housed in a large grey hammerite metal case that measures approx. 49 x 36 x 34 cm and weights about 36 kg. At the bottom of the case is a shock-mount base, allowing the device to be used in a mobile environment, e.g. as part of a mobile intercept station. although transistors were widely available when the R-355 was developed, all circuits are built with valves (tubes).

The most basic setup with an R-355

The device was typically used in combination with a Russian R-250M communications receiver and a P-181 disc recorder as shown in the diagram above, but other combinations were also possible. Furthermore, the R-355 was capable of controlling an external transmitter, such as the R-830, the R-820M, the R-118BM and the R-357, in order to allow two-way communication and handshaking (message acknowledgement). The R-355 itself consists of five functional blocks:
  1. Oscilloscope
  2. Switching and auto-start
  3. Automatic search and selection
  4. Front panel with remote control
  5. Power Supply Unit
The front panel acts as the central part of the R-355. It contains all controls of the other four blocks and hold the oscilloscope display. Furthermore it holds the connections (at the front right) to the external devices that it controls as well. The Power Supply Unit (PSU) is the heaviest part of the R-355. It supplies no less than nine different voltages to the various part of the device.

The diagram above shows how the various blocks are related. The receier (RX) is shown at the top left. In most cases, a Russian R-250M receiver was used in this position. The transmitter is optional and is used for message handshaking. In situations were a spy radio set with an automatic burst transmitter was used at the far end, the radio would first send a pilot tone, the R-355 would then answer with a handshake tone, after which the spy radio set would start transmitting the message, whilst the R-355 recorded it on an external disc or tape recorder. At the end of the transmission, the recorder was stopped automatically by the R-355 again.
P-181 Disc Recorder
In the early years, the high-speed morse-coded burst transmissions were recorded onto a P-181 disc recorder. The P-181 was one of the first recording devices in the USSR that used a ferro-magnetic disc rather than a tape. It was developed and built in 1957 by VNAIZ (ВНАИЗ) [3]. 1
The device resembles an ordinary gramophone with a turning table and a pickup arm, but rather that vinyl discs, it used ferro-magnetic discs. As such it was not a simple play-back device, but was able to record audio onto such discs as well.

The image on the right shows a typical P-181 as it was on display at the Polytechnic Museum in Moscow in 2009 [4]. The device was especially designed for the recording of morse signals with a variable turntable speed between 35 and 100 rpm. Apart from the needle, the pickup head contains a combined recording and playback head. The discs were ereased separately.
P-181 magnetic disc recorder. Copyright Valery G. Kharchenko [4].

The gaps between the tracks are rather wide. At the maximum speed of 100 rpm, the device can record upto 1.5 - 2 minutes of audio. As the inner tracks of the disc are shorter than the outer tracks, and the rotation speed is constant, the absolute speed of the inner tracks is lower. As a result, the maximum audio frequency decreases towards the end of the disc. On the first track, the audio bandwidth is 300 - 5000 Hz, which decreases to 300 - 3000 Hz at the end.

The P-181 was remotely started and stopped by the R-355 at the beginning and the end of a received burst transmission. The P-181 is also known as the MAG-D1 (Russian: МАГ-Д1).
  1. VNAIZ (Russian: ВНАИЗ) was the USSR Scientific Research Institute for Recording, which was established in 1934 as the Central Research Laboratory of Gramophone. In 1963, the intitute was renamed to VNIIRT (ВНИИРТ), the Insitute of Megnetic Recording Technology and Radio and Television Broadcasting. In 1970, it was renamed to VNIITR - Institute of Television and Radio (Russian: ВНИИТР), which in 1996 became a public company. In 2009 the name was changed once more into ZAO VNIITR (Russian: ЗАО ВНИИТР) [3].

Interior of the R-355

The interior of the R-355 can easily be accessed by loosening the four large red bolts at the four corners of the front panel. This allows the front panel to be pulled forward and removed from the case. Three functional blocks (1, 2 and 3) are mounted to the rear of the front panel (block 4).
When removing the front panel, the rather heavy Power Supply Unit (PSU) stays behind in the empty case. It is normally connected to the front panel through a large brown connector, that carries all the voltages, at the front of the PSU.

The image on the right is not the skyline of New York, but the interior of the R-355. It becomes visible when the front panel is turned on its face and consists of functional blocks 1 (display unit), 2 (control unit) and 3 (search and select). Each of these blocks is contained in a metal enclosure with the valves, relays, etc. mounted at the back.
R-355 interior

Although the manuals that came with our R-355 were released in 1974 and 1977, the presence of valves and the absence of transistors suggest that the device was designed during the late 1950s, or the early 1960s at the latest. The device is well designed and the removable parts are easily accessible. The valves and relays are all socketed and the valves are protected by spring-loaded cylinders to prevent them from falling out of their sockets.
Opening the case R-355 interior Rear view of the meter and the meter selector. At the front are the various sockets. CRT socket Close-up of one of the valves R-355 interior detail R-355 interior detail PSU in the empty case, after removing the interior

The R-355 was supplied with full instructions for its installation and use. At least two manuals are required for a good understanding of the system. The first one is the Technical Description and Operating Instructions [1]. The second one is for the technically minded, and contains the Component List and Circuit Diagrams [2]. A complete setup is described in the first manual.
The manuals in our collection were released in 1977 and 1974 respectively. Unfortunately, they are only available in Russian and so far we have not found a translation into any other language.

These manuals have East-German (DRR) stamps on each page. During the Cold War the R-355 was CONFIDENTIAL (German: Vertrauliche Verschlußsache), but this has since been lifted. Each year and each time something was added, a new stamp was added to the first page. The oldest stamp in the manual is from 20 April 1982 and the last one is from 4 October 1988.
Circuit diagram of the oscilloscope

It suggests that this particular R-355 was used for more than six years, but it is entirely possible that the device is older and that at some stage the manuals were updated and replaced. It is also possible that the device was kept as spare in a distribution centre and that it was only checked periodically. In any case, the manual proves that the R-355 was also used outside the USSR.
Technical manuals Technical manuals Secret! First page of the manual Close-up of the stamps on the first page Random page from the manual Random page from the service manual Circuit diagram of the oscilloscope

All sockets for connection of the peripheral equipment are located at the right front of the R-355, just off the right edge of the control panel. There are three coaxial PL-259 sockets and two large black multi-pin sockets. Another multi-pin socket is located at the rear of the device. It is used for connection of the AC mains power lead. At the left front, just left of the front panel is the service test socket. In normal use, a shorting plug should be present in that socket.
# Text Socket Type Description
1 Н/ОМ ПЧ П-250М Ш4-8 Input 2nd IF from R-250M
2 НЧ 1-26 кГц Ш4-9 Output Audio (to tape recorder)
3 АРУ Ш4-7 Output Peak amplitude signal (AGC)
4 ЛСЭ Ш4-13 Multi Transmitter Control (see below)
5 МАГ. Ш4-10 Multi Tape Recorder (see below)
6 КЛЮЧ Ш4-12 Banana Morse key
7 ТЛФ Ш4-11 Banana Headphones
8 ОСЦИЛ. Ш4-6 Circular Service socket (see below)
9 СЕТЪ Ш5-1 Multi 127 or 220 V AC Mains (see below)

Phones and morse key sockets. At the right the black socket for the tape recorder. The service socket at the top left Top left corner with the service socket AFC switch, headphones socket with volume control, and morse key socket Audio output Mains socket at the rear Connections at the right side of the R-355 Peripheral sockets at the right corner Peripheral sockets at the right side PL-259 sockets
Input: 2nd IF from R-250M AGC output Audio output Transmitter socket Tape recorder socket Mains socket at the rear Cable for connection of a tape recorder to the R-355 Close-up of a multi-connector

Ш4-13   ЛСЭ - Transmitter Control
  1. Audio out to transmitter (0.2V into 100 kOhm)
  2. Signal Ground (GND)
  5. PTT voltage output (+24V during TX)
  8. Potential free PTT contact (with pin 10)
  9. Potential free PTT contact (with pin 9)
Ш4-10   МАГ. - Tape Recorder
  1. Potential free REC contact (with pin 2)
  2. Potential free REC contact (with pin 1)
  3. Audio out to recorder (regulated)
  4. GND 
  5. GND
  7. AC Mains power (with pin 10)
  9. GND
  10. AC Mains power (with pin 7)
Ш4-6   ОСЦИЛ. - Service Socket
  1. Oscilloscope horizontal input
  2. Oscilloscope vertical input
  4. Signal (normally shorted to 2)
  7. GND
Ш5-1   СЕТЪ - AC Mains
  1. ~
  2. ~
  3. ~
  4. 0
  5. 0
  6. 0
Technical specifications
  • Storage temperature: -50°C to +65C
  • Operating temperature: -10C to +50°C
  • Humidity: 98% @ 40°C
  • Maximum power consumption: 130 W.
Internal voltages
  • +340 V, 26 mA (anode voltage)
  • +250 V, 15 mA (anode voltage)
  • +150 V, 10 mA (stabilized anode voltage)
  • -700 V, 1 mA (cathode ray tube voltage)
  • +24 V, 300 mA (relay supply voltage)
  • 6.3 V, 5 mA (filament power)
  • 6.3 V, 770 mA (timebase generator filaments)
  • 6.3 V, 590 mA (cathode ray tube filamament)
  • 3 V, 0.5 mA (backlight)
Valves (tubes)
  • 4 x 6Н2П-ЕВ
  • 1 x 6Н3П-Е
  • 2 x 6К4П-ЕВ
  • 4 x 6Ф1П
  • 2 x 6Ж1П-ЕВ
  • 1 x 6П15П-ЕВ
  • 2 x 6Х2П-ЕВ
  • 1 x CRT: 8ЛО29И
  • 2 x Zener: СГ2С
  • 1 x Zener: СГ1П-Е-В
АПЧ   Automatic Frequency Control (AFC)
АРУ   Automatic Gain Control (AGC)
ЗАПИЦЪ   Record
НЧ   Intermetiate Frequency (IF)
ТЛФ   Headphones
ТЛГ   Telegraphy (morse)

  1. R-355 Technical description and Operating Instructions (Russian)
    Прибор Управления и Контроля Р-355.
    ИВ2.029.004 ТО/С. 1977.

  2. R-355 Component list and circuit diagrams (Russian).
    Прибор Управления и Контроля Р-355.
    Приложение (supplement). 1974.

  3. All-Russian Research Institute of Television and Radio
    Website (Russian). Retreived June 2014. Valery G. Kharchenko,

  4. Image of P-181 magnetic disc recorder
    Website: 20th Century Domestic Radios (Russian). Photograph taken at the Polytechnic Museum in Moscow (Russian in 2009). Retrieved June 2014.

Further information

Any links shown in red are currently unavailable. If you like this website, why not make a donation?
Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Friday, 20 June 2014 - 17:41 CET
Click for homepage