Radio communication: printing (un)coded telex messages with the SCRIBOPHYL (1961)

Printing (un)coded telex messages with the SCRIBOPHYL (1961)

At the end of the fifties of the twentieth century, the Royal Netherlands Airforce 45th telecommunication service wanted to record intercepted encrypted and unencrypted military telex messages stemming from behind the iron curtain. In 1960, custom-built papertape punch machine PunchroPhyl was developed by TNO that could capture the received telex messages in papertape. This device was able to create 7-hole (4 and 3 tracks around the s [sprocket row) paper tape with the layout shown below.

Seven-hole papertape punch layout
Seven-hole papertape punch layout

A reader-decoding device was developed for reading the recorded communication. The device had four exchangeable read screens (Russian Siemens Code 7½ bits (RSC), Russian Machine Code 7 bits (CT35), Russian Baudot Code 12 bits (RBC) and the International Code Nr2 7½ bits (CCIT2)). The selected one was placed in the device. By foot pedal operation, the punched tape to be decoded moved in a Siemens punch tape reader which was connected to the device. The characters that appeared on the screen could then be noted on paper.

Reader-decoding device
Reader-decoding device

 

Siemens telex papertape reader/punch device
Siemens telex papertape reader/punch device

The printing of the messages was shortly later in 1961 another device developed, the SCRIBOPHYL (Typewriter with Cyrillic alphabet for Russian, International and Baudot Transfer Systems, PHYsic Laboratory).

To print the recorded messages, a custom-built digital controller for a typewriter called SCRIBOPHYL (Printer with Cyrillic alphabet for Russian, International and Baudot Transfer Systems, PHYsic Laboratory) was developed in 1961. SCRIBOPHYL processed the paper tapes with the encrypted and plain text telex messages. With the SCRIBOPHYL, partly built into a “standard government bureau”, telex messages could be processed in every existing telex code and printed on paper. Most telex codes use five information and two synchronization bits (papertape holes). With the information bits, 32 different characters can be displayed. First of all, the letters of the alphabet and some signs for the wagon functions of the telex equipment. To be able to transfer more information with the five bits, there was one five-bit combination reserved to switch to character mode and one combination to go to number/punctuation mode. Until a mode shift, the mode stayed constant: letter mode or number/punctuation character mode.

The SCRYBOPHYL
The SCRYBOPHYL

A different telex code is the Baudot code. It consists of ten information bits and two synchronisation bits. It is a so-called multiplex system of two telex channels. The first five bits belong to channel I, the next five bits to channel II. In the PUNCHROPHYL papertapes, the code combinations for the channels I and II were punched successively. To read the information from one channel, the alternate characters had to be read.

The intercepted telex messages could be accommodated in the paper tape in various ways.

  1. Plain text telex messages:
    • Messages in telex codes for paper printers.
      These are telex codes which include the device functions “return carriage” and “new line”:

      1. International code number 2 (CCITT number 2).
      2. The Russian Siemens code (R.S.C.).
      3. Russian national code with positive character (RNC +).
      4. Russian national code with negative character (RNC -).
    • Messages in telex codes for papertape punchers.
      These codes do not contain a “return carriage” and “new line”. These codes can be divided into five-bit and ten-bit telex codes:

      • Five-bit telex codes
        • Russian ST35 code with Russian alphabet (R–CT35).
        • Russian ST35 code with Latin alphabet (R-ST35). A special feature of the Russian ST35 is that a different code combination for the character “letters” was used for the Russian and the Latin alphabet. With that character, it was possible to deduce in which alphabet the Russian ST35 code had been set.
        • The Czech ST35 code (T–ST35).
        • The Polish ST35 code (P–ST35).
      • Ten bits telex code: The Russian Baudot code (R.B.C. or MKT-2). With the Baudot code, code combinations for letters and numbers have a double function. Both are also used as spaces. The code has three shift modes. The Cyrillic alphabet starts with a 00000 character. Because it has more Cyrillic characters than the Latin alphabet, the characters!, &, £ and the bell have been replaced by Cyrillic characters. Which characters were added to the code combination in the various telex codes is shown in FIG. 1.
  2. Encrypted messages:
    • Encrypted messages with carriage functions (equipment functions). The coded messages with carriage functions could be displayed in the sent telex codes. A particular layout was then included in the message. For this purpose, the message was divided into groups of 4, 5 or more characters. These characters were generally written in letters or numbers.
    • Encrypted messages without wagon functions. These messages were displayed in 32 different code combinations (5 bits = 25). The telex transmitters, from which these messages came, broadcast characters (code combinations of five bits) at a constant frequency. Contained a sign information, then that was in the with the PUNCHROPHYL papertape by a punched hole in the sixth track. A mark contained no information if this particular sixth track had not been punched. The sign always had the code combination: 00000. This was called a sign without information, the so-called “idle-time” character. To record the coded messages without carriage function, 7-track punch tape was used. When these coded messages were generated in the Baudot code, only the channel I sign indicated whether one of the two channels contained information. The “CRYPTO” function on the “SCRIBOPHYL” control panel has been activated for these coded messages without a carriage function. For other messages that was the function “READY”.
      SCRIBOPHYL codes
      SCRIBOPHYL codes

      The table in (Fig.2) makes clear that a sign from the letter shift is not linked together with a sign from the number shift. For example, in the CCITT-2 code alphabet the A merges with the – sign, while in the R.B.C. code list the A goes with the number 1. There are 32 letter and 32 number combinations possible. The characters, which are stored in the different telex codes in the LETTERSHIFT mode, can be displayed in one shift position of the electric typewriter. The characters of the FIGURE SHIFT can be displayed with the other shift mode of the electric typewriter.

The PUNCHROPHYL papertape was read with a paper tape reader. The characters read appeared in a five-bit register of the “SCRIBOPHYL”. If the tape reader read a character, that character was stored in a memory (one bit shift memory). A number character erased the memory. The memory element set the shift position for the typewriter. Together with the five-bit information register, the one-bit shift memory formed a 6-bit character. This enabled a total of 32 letter combinations plus 32 number combinations to be printed. A code converter converted the 6-bit code into a signal on one of the 64 outputs (32 for letters plus 32 for digits). These outputs were linked to the entry side of a code card. A code card was developed for each kind of telex code. Via this code card, the incoming signals were converted to the output side via the code converter. With the converted 6-bit information, a single typewriter coil was energised. The letter, number or punctuation mark symbol associated with this coil was then printed on paper. The code cards were two-sided circuit boards with printed wiring. These printed circuit boards were equipped with 64 input and 56 outgoing contact paths. The incoming lines could be connected to every outgoing line. By placing a code card for a particular telex code in the SCRIBOPHYL, a telex message could be printed on paper. The incoming signals on the code card were thus connected to the correct outgoing lines of the code card. In order to reduce the number of code card exchanges, four code cards were simultaneously present in PCB holders that were built into the desk drawer. The selection for a specific code card was carried out with a switch on the control panel.

Encrypted telex messages

As stated above, encrypted telex messages contain 32 different characters. These characters were represented by 32 different characters using the letter shift. With the SCRIBOPHYL, it became possible to display a received encrypted telex message written in any of the telex codes. If we presented a crypto message bin the telex code for the Latin alphabet, then the wagon functions and five work (= code combination 00000) of the typewriter were replaced by Russian letters which do not appear in the Latin alphabet. Conversely, with such a telex message in the telex code for the Russian alphabet, the typewriter wagon functions and five work were replaced by Latin letters which in turn are not present in the Russian alphabet. In this way, there was an exchange for the wagon functions with non-existent codes for the selected alphabet. The letters used for the typewriter wagon functions and the five work are included in the table below.

Replacement codes
Replacement codes

Only the characters with information were written with the typewriter. As previously discussed, the information in track 6 of the papertape provided for this. The control of the typewriter provided a layout in groups of 3, 4 or more characters so that encrypted messages stood out. In order to be able to make notes next to the groups, the horizontal distance between the groups to be written was made adjustable, for example: abcd pqrs tuvw xyza aklm nijm fgps aouy

This format had the advantage of discovering equal parts or certain patterns in the text (the message) faster. This facilitated deciphering the crypto messages. The format to be used was derived mechanically from the position of the tabular rail of the electric typewriter. This was easy to set up with the set and reset button of the typewriter.

It could also happen that the paper tape was punched by the PUNCHROPHYL in an inverted way. The 1 was punched as 0 and a 0 was punched as 1. Inverting backwards could be done by the SCRIBOPHYL.

The SCRIBOPHYL design

Papertape reel winder/reader

In order to be able to operate the paper tapes, there was a fast papertape winder/reader capability. This device could keep the paper tape tensioned while reading the papertape. It was also possible to quickly wind the reels left or right. Fast-forwarding became necessary when long information-free parts were present in the punched paper tapes. Fast-forwarding prevented loss of time. It was also possible to go quickly to the beginning of a papertape. This was important for processing information that was punched in the two-channel Baudot code.

Papertape winder/reader
Papertape winder/reader

Technical design of the SCRIBOPHYL

The following units can be distinguished in the drawing (numbering at the top right of each of the blocks):

  • Input (no. 1, 2, 3 en 4)
  • The code converter (no. 5, 6, 7, 8, 9, 10 and 11)
  • The electric typewriter and controller (no. 12 en 12a)
  • The system clock with control (no. 13)

The input consists of:

  1. The paper tape reader (No. 1) with a reading speed of up to 25 characters/second mechanically scanned the tape. A punched hole was placed in a register as a high signal (a ‘1’). A blank part (no punched hole) was accommodated as a low signal (a ‘0’). The papertape reader was provided with a “tape-out” contact. The SCRYBOPHYL could thus be stopped.
  2. The punch tape rinsing machine (no. 2) provided the supply and discharge of the paper tape to be read to and from the read head. The device was also equipped with a tight-band contact. This stopped the SCRYBOPHYL when the punched tape feed failed.
  3. Control of the paper tape reader (No. 3).
    The transport speed of the reader was determined by the maximum speed of the electric typewriter (10 characters/s). The controller for the reader gave 10 pulses/s when reading 5-bit punched tapes and 20 pulses/s when reading 10-bit (Baudot-code) punched tapes. In the case of paper tapes in Baudot code, the other character was read (in the register). The code card to use (number 7 in the diagram) set the speed of 10 or 20 pulses/s. Also driven by the code card, the system clock with its control (number 13) provided the impulses for the control of the paper tape reader.
  4. The read register (nr. 4):
    The system clock with control wrote the read characters in the read register. For the Baudot code, only the characters of the selected channel were read. Together the read register and the shift memory set the relay tree (number 5).

The code converter consists of:

  1. Relay tree (No. 5): The relay tree converted the 6-bit information for a connection from the typewriter controller (No. 12a) to one of its outputs. With that, an impulse appeared, generated by the typewriter control at this output.
  2. Selector switches (No. 6) that connect the outputs of the relay tree to the inputs of the selected code card (one of the four slots). The code card selection was done with one of the four push buttons on the right side of the control panel.
  3. Code cards (nr. 7):
    • The code card connected the relay tree outputs to the write coils of the typewriter. The connections on the code card were made in such a way that the correct letter or number was printed on paper.
    • The code card has a fixed program setting, which determines the type of code to be processed. The following program settings could be included on a code card:
      • Baudot code / no Baudot code. After choosing the Baudot code, the paper tape reader read at an increased speed of 20 characters/s. One channel was then read. The corresponding codes for letters and numbers have a space.
      • Latin / Russian. In the “CRYPTO” position, wagon functions in the Latin telex code were converted to Russian characters. The carriage functions and “five work” of the Russian alphabet were in turn replaced by Latin characters.
      • ST35 code / no ST35 code. With a ST35 code, a mark was made when switching from Latin to Russian alphabet and vice versa.

      In the attached table the numbers of the outputs on the code cards indicate which letter, number or car function they belong to.

      The letter, number or carriage function of each of the 52 outputs on the code cards
      The letter, number or carriage function of each of the 52 outputs on the code cards
    • Shift memory + control (No. 8).
      The electric typewriter was not equipped to be placed on the letter command in the numeric shift. For the letter shift, the shift coil of the typewriter was continuously energized. When the shift coil was not energized, the typewriter was in the digits shift position. A memory element was required to set the shift. This shift memory was controlled by the “Ready / Crypto” switch positions on the control panel. The shift memory set the 6th bit for the relay tree and thus controlled the shift position of the typewriter.
    • Crypto / ready switching (No. 9).
      The SCRIBOPHYL in “Crypto” mode was used for encrypted messages without a car feature. The others were writing in the “Ready” position. In “Crypto” mode, the circuit switched the typewriter to “Letters” and replaced the carriage functions with letters. The circuit also took care of the layout of these written letters.
    • Baudot double function (no. 10).
      In Baudot code, the code combination for numbers and letters corresponds to that of the space. The Baudot double function circuit ensured that the function letters/digits and the function space were sent to the typewriter as a blank command.
    • CT / ST35 marking (No. 11).
      In the ST35 (CT35) coding, two code combinations for the transition to characters were used. One in Latin and one in the Russian alphabet. If, when typing the typewriter on the control panel, a light was on, the type of alphabet used did not match that of the code card. By pressing the “CT / ST35” button, once a different alphabet (another code card) was chosen, a letter was printed on the paper as recognition of the transition to the other alphabet.

The IBM typewriter with its controls:

  • The writing speed was standard: 10 characters/s. The writing and carriage functions received the typewriter from its control system. The shift command was provided by the shift memory. The impulses for the IBM control did not coincide with the switching of the relays in the relay tree. This is to prevent interference from the relays. A feedback from the typewriter stopped the system clock when the execution of a carriage function on the typewriter lasted longer than 100 milliseconds. A microswitch was connected to the setting for the right-hand line on the IBM typewriter. This arranged the automatic return trolley and new rule. A microswitch was also fitted on the tab rail. This controlled the tabulation spacing of the printing of encrypted telex messages.

The system clock and clock control:

  • The system clock provided for all control pulses required for the circuits mentioned above The setting of the clock and the clock control was determined by the selected code card. When crypto messages were processed, the whether or not printing a character with the typewriter was determined by the information in track 6 of the papertape. The typewriter function of the typewriter stopped the system clock for as long as this function lasted.

 


Background: papertape

The perforated tape consisted of a paper band (strip), in which the information is encoded in round holes were punched, arranged in five or eight rows. From the early 1950s to the end of the 1970s, it was a widely used computer medium for both data and software storage. The paper tape strip was about 2 cm or 2.54 cm (inch) wide. The mechanical specifications, which both the unpunched and punched paper strips had to comply with, were laid down in the so-called ECMA standard 10 (ECMA-10) (ECMA-10). This standard was maintained until the mid-70s of the twentieth century.

8-hole papertape was available in any colour
8-hole papertape was available in any colour

In five-hole papertape, the five information bits were written perpendicular to the tape, three on one side and two on the other side of the smaller transport holes (so-called sprocket holes). Because five bits (holes) were too little for data storage, the storage on the paper tape was later enlarged to 8 holes in a row (five and three). In the eight-hole papertape, so-called ASCII characters were punched either 6, 7 or 8 bits of data. Many coding methods were in use. In order to deal with errors in punching and reading, there was sometimes a parity bit added. This special bit, recorded in one row, caused the total sum per column to be odd. The paper tape reading device stopped when an even number of holes were read. It was then up to the operator to ascertain the error and record it by means of a note on the print report.