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Tempest PSU
Fialka power supply unit

As far as we know, two different power supply units have been used in combination with the Fialka cipher machine. One is a rather simple variant, whilst the other one contains advanced counter measures against the exploitation of unwanted eminations (also known as TEMPEST).

The one shown here is the TEMPEST variant, marked БПК-125, which has thusfar only be found in combination with Fialka machines in Poland, which is why it is sometimes referred to as the Polish Fialka PSU. Other countries, such as the former DDR, used the standard PSU.

The TEMPEST PSU measures about 28 x 19 x 17 cm and was designed especially for use with Fialka. It is suitable for both Fialka models (M-125 and M-125-3). It is connected via three cables: one at the front for connection to the 110V or 220V AC mains, and two at the rear.
  
The TEMPEST Fialka PSU (as used in Poland)

The two cables at the rear should both be connected to the Fialka. A thin cable provides the necessary 24V DC voltage for running Fialka, whilst a thick cable connects the PSU to the 5-bit digital output at the right side of the Fialka. This connection to the digital data output is mandatory as it activates the TEMPEST measures inside the PSU. This is achieved by a small switch that is mounted in the data connector. Without this connection, Fialka will not run.

The closed PSU with covers at the font and rear The cables stored in a compartment at the right side TEMPEST PSU with the front and rear covers taken off The TEMPEST Fialka PSU (as used in Poland) The 3 cables that are needed for a proper connection The PSU placed to the left of the Fialka The PSU placed to the right of the Fialka Rear panel of the Fialka TEMPEST PSU
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The closed PSU with covers at the font and rear
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The cables stored in a compartment at the right side
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TEMPEST PSU with the front and rear covers taken off
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The TEMPEST Fialka PSU (as used in Poland)
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The 3 cables that are needed for a proper connection
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The PSU placed to the left of the Fialka
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The PSU placed to the right of the Fialka
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Rear panel of the Fialka TEMPEST PSU

Controls
All controls of the TEMPST PSU are at the front panel. The switch at the bottom left is used for selecting the correct mains voltage range and for switching the device on or off. A ring with an excentric disc protect this switch against setting it to the wrong voltage (more about this below).

Above the mains voltage selector is a 3-position primary voltage adjustment and - above that - the 10-position secondary voltage selector. Above this selector are the primary (3A) and secondary (5A) fuses. These are typical Russian fuses that may be a bit hard to obtain.


The section at the top is for checking the functions of the PSU. When the PSU is in use, the meter at the top center should read between 50 and 60. This indicates a nominal output voltage of 24V DC. The two check switches are used for checking the currents and the TEMPEST feature. The STROBE light, to the right of the meter, is also for checking the TEMPEST feature (more below).

Connections
The socket for connection to the mains is at the front right of the PSU. All other connections are at the rear, where four sockets are present. The leftmost one (marked МАШИНА I) is the 24V output for Fialka. The rightmost one (marked МАШИНА II) is for connection to Fialka's data output. If Fialka is normally connected to a transmitter or telegraphy device, that device should now be connected to the center socket at the rear of the PSU marked ВЫХОД (output).


Although it may seem unnecessary, the data socket (marked МАШИНА II) must be connected, as otherwise the machine will not work. This is done to ensure the use of the TEMPEST feature (see below). An extra 24V DC output socket is available at the bottom. This 2-pin socket can be used for connection of an extra device, such as a work light or an extra Fialka machine. In the latter case, the TEMPEST features are not used for the additional machine, of course.

Fialka TEMPEST PSU front panel Fialka TEMPEST PSU rear panel Connecting a work-light to the rear of the PSU
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Fialka TEMPEST PSU front panel
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Fialka TEMPEST PSU rear panel
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Connecting a work-light to the rear of the PSU

Cables
In order to use the TEMPEST PSU in combination with a Fialka machine, a minimum of three cables are needed: a mains power cable, a 24V DC cable for feeding Fialka, and a data cable. These cables are usually stored inside the cable storage compartment at the right side of the PSU.

The hinged lid to the cable compartment is held in place by two screws that can be loosened by hand or, if they are really tight, with the aid of a screw­driver. If the cables are present, it may be a bit difficult at first to get them out of the storage compartment as the cables will be rather stiff.

Be carefull with these cables as they might have become fragile after all this time. Once you got them out of the storage compartment, it is probably best to leave them out and store them separately with the PSU in the future. This will protect the cables against too much bending.
  
The 3 cables that are needed for a proper connection

For safety reasons, it is advised to thoroughly check the mains power cable before connecting it to the mains. As the cable is rather old, the insulation of the internal wires may have become brittle and might have to be replaced. Use the mains cable only if you are certain that it is safe.

The data cable is something truely special. It is a vital part of the TEMPEST feature of this PSU and allows the PSU to monitor the 5-bit data stream created by the Fialka. One side of this cable holds a 10-way data connector that fits the digital data output at the right side of the Fialka.

A switch, that is mounted at the base of this plug, senses whether the plug is placed in the socket and activates a relay inside the PSU. This relay switch the 24V output of the PSU on. This is done to ensure that the cable is in place and that the TEMPEST safety measures are used.
  
Data cable Fialka-end (note the small switch at the right)

At the other end of the data cable is a rather large circular plug that should be connected to the МАШИНА II socket at the rear of the PSU. If this cable is missing, it is advised to build a suitable alternative before continuing. The remaining cable simply connects the 24V DC output of the PSU to the 24V DC input at the left side of the Fialka.

The closed PSU with covers at the font and rear Opening the cable compartment The cables stored in a compartment at the right side The cables stored in a compartment at the right side The 3 cables that are needed for a proper connection Mains AC cable 24V DC power cable for Fialka Data cable
Mains AC power plug 24V DC connector for powering Fialka Connecting the 24V DC supply to the Fialka Data cable PSU-end Data cable Fialka-end (note the small switch at the right) The data cable connected to the data socket of the Fialka The 24V relay that blocks the power output of the data cable is not present The PSU placed to the left of the Fialka
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The closed PSU with covers at the font and rear
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Opening the cable compartment
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The cables stored in a compartment at the right side
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The cables stored in a compartment at the right side
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The 3 cables that are needed for a proper connection
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Mains AC cable
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24V DC power cable for Fialka
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Data cable
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Mains AC power plug
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24V DC connector for powering Fialka
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Connecting the 24V DC supply to the Fialka
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Data cable PSU-end
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Data cable Fialka-end (note the small switch at the right)
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The data cable connected to the data socket of the Fialka
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The 24V relay that blocks the power output of the data cable is not present
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The PSU placed to the left of the Fialka

Using the PSU
The PSU can be placed either to the left or to the right of the Fialka. It can also be placed behind the machine or on a shelf. The various cables should just be long enough for that. Before connecting the power supply unit (PSU) to the Fialka, you first need to check the voltage settings on the device, and adjust them if necessary. First check the setting of the ВЫКЛ switch at the bottom left of the front panel and ensure that it matches your mains AC voltage (127 or 220).

This switch can be altered by unscrewing the ring and rotating the excentric disc at the center by 180°. The centre setting of this switch turns the PSU off. For most European 230V networks, you should set this switch to 220V. If your mains voltage is slightly lower or higher, you may compensate for this by setting the toggle switch at the center to МЕНЬШЕ (less) or ВОЛЬЕ (more).

For 230V networks - which is common in Europe nowadays - this switch should be set to МЕНЬШЕ (less - i.e. the leftmost setting). It prevents the mains transformer from going into saturation.

Ensure that the PSU is switched OFF (ВЫКЛ set to the centre) and connect the Fialka to the two sockets at the rear of the PSU. A thin cable connects the PSU socket МАШИНА I to the 24V DC input at the left side of the Fialka. A thick cable connects PSU socket МАШИНА II to the data output at the right side of the Fialka. Ensure that the Fialka itself is switched off at this stage.
  
The PSU placed to the left of the Fialka

Now connect the PSU to the mains by supplying the mains AC voltage to the СЕТЬ socket at the front right and then turn the PSU on (leave Fialka off at this stage). Ensure that the meter at the top shows a reading between 50 and 60. If it is higher or lower, use the rotary switch at the centre to adjust the voltage. When it is within the required range, it is safe to turn the Fialka on.

At this stage, the motor of the Fialka should start running. If it doesn't, there might be a special condition: the motor may be blocked (engine grease has dried up), one of the fuses in the Fialka may be broken, or one of the fuses of the PSU may be blown. When the Fialka is running, the primary current within the PSU can be checked by pressing (and holding) the leftmost push-button on the PSU, marked КОНТРОЛЬ I. The meter should show a reading between 40 and 90.

Likewise, the secondary PSU current can be checked by pressing (and holding) the rightmost push-button, marked КОНТРОЛЬ II. It should give a reading between 80 and 90. Now press a key on the Fialka keyboard, whilst still holding down КОНТРОЛЬ I or КОНТРОЛЬ II. The STROBE light to the right of the meter should flash briefly. If it doesn't, there might be something wrong with the thick data cable between the Fialka and the PSU. The STROBE light indicates the presence of the STROBE signal on the data cable and confirms that the TEMPEST circuit is operational.

Removing the ring from the mains voltage selector Altering the setting of the voltage selector Switching the PSU off Switching the PSU on Thin cable between PSU and Fialka Tick cable between PSU and Fialka Power cable connected to the mains input at the front of the PSU Connecting the 24V DC supply to the Fialka
The data cable connected to the data socket of the Fialka The meter at the top showing a reading between 50 and 60 Close-up of the controls and checks at the front panel Checking the primary current Checking the secondary current Checking the primary fuse The PSU placed to the left of the Fialka The PSU placed to the right of the Fialka
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Removing the ring from the mains voltage selector
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Altering the setting of the voltage selector
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Switching the PSU off
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Switching the PSU on
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Thin cable between PSU and Fialka
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Tick cable between PSU and Fialka
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Power cable connected to the mains input at the front of the PSU
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Connecting the 24V DC supply to the Fialka
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The data cable connected to the data socket of the Fialka
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The meter at the top showing a reading between 50 and 60
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Close-up of the controls and checks at the front panel
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Checking the primary current
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Checking the secondary current
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Checking the primary fuse
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The PSU placed to the left of the Fialka
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The PSU placed to the right of the Fialka

Circuit description
The circuit of the TEMPEST PSU is extremely complex and difficult to trace. Roughly speaking we can device the circuit into three functional blocks: the transformer, the stabilizer and the TEMPEST circuit. This is illustrated in the simplified circuit diagram below:


At the left is the mains transformer, which has several taps at the primary side in order to adjust it to the local mains voltage. The output voltage can further be adjusted with a 10-position rotary that selects the appropriate secondary tap. After rectifying the secondary voltage, a stabilizer circuit converts the raw 29V DC into a more stable 24V DC that is suitable for driving Fialka.

The block at the far right is the TEMPEST circuit. It consist of five identical sub-circuits; one for each bit of the 5-bit digital data output of Fialka. The simplified circuit diagram below shows how it works on one of the bit-channels. To the left of the dashed line is the output circuit of one of the data bits of the Fialka. This circuit (T1) drives the printer/puncher solenoid (S1).


To the right of the dashed line is the input circuit of a single bit of the the PSU. Whenever the solenoid (S1) is activated, transistor T2 is not conducting and the dummy-load resistors are not driven. As soon as S1 is realeased (i.e. the bit is not driven), T2 starts conducting and the dummy-load resistors are activated. There are five identical circuits; one for each bit.

The value of the dummy-load resistors is choosen carefully, so that they the circuit draws the same current as the solenoids. As a result, the PSU will not only supply a constant voltage, but will also consume a constant current. This way, an eavesdropper can not obtain any valuable information by tapping the mains power line (TEMPEST).

Wiring of the cables and sockets
One of the most important cables is the thick data cable, that connects the 5-bit digital output of the Fialka to the PSU, to that it can monitor its activity and enable any of the internal dummy-loads. If the cable is missing, use the diagram below to create an alternative:


The data connector at the right is shown looking into its pins. It has 10 pins, all of which are wired. The numbers at the end of the arrows correspond with the numbers of the pins of the large circular connector. Please note the switch that is built into the base of the data connector at the right. It will be activated (i.e. closed) as soon as the plug is inserted into the data socket of the Fialka. It is wired to the large connector via two additional wires (18 and 19).


For completeness, the pinout of the data socket at the right side of the Fialka is given here as well. It is identical to the data socket at the rear centre of the PSU and is wired straight through. As the data socket on the Fialka will be used by the PSU, any external device (e.g. a transmitter or a telegraphy device) should be connected to the PSU instead.

Interior
The interior of the PSU can be accessed by removing the two side panels and the bottom panel. The side panels are held in place by two screws at either side of the PSU. After removing the two screws, the side panel can be removed. Other other side panel can be removed in the same way.

At the right side, the grey mains transformer is immediately visible. Below the transformer is an array of five capacitors that are connected in parallel. Some of the power transistors are mounted to the rear panel for sufficient cooling.

The other side of the PSU holds a large brown printed circuit board (PCB) that contains the electronic circuits. Apart from the 24V stabilizer, this board contains the TEMPEST circuit. The dummy-load resistors are visible as an array of resistors at the top edge of the board. The actual TEMPEST circuit itself is located in a corner.
  
PSU circuit detail

Also on this PCB is the STROBE sensing circuit that enables the TEMPEST circuit whenever the user presses a key on the Fialka keyboard. This circuit also drives the STORE check light, to the right of the meter a the front panel. In some of the circuits, 2TC613 ICs are used [1]. Each of these ICs contains four transistors, They belong to one of the first generations of Russian ICs. Behind the transformer is a relay that switches the 24V output. It is activated by the data connector switch.

Opening the case Removing the side covers from the PSU TEMPEST PSU with its side panels removed TEMPEST PSU interior seen from the right PCB inside the PSU PSU interior seen from the right PSU circuit detail Removing the PCB
Interior of the PSU with the PCB folded away The 24V relay that blocks the power output of the data cable is not present Dummy-load resistor array The five dummy-load driver circuits Close-up of the STROBE-sensing circuit Russian IC on the PCB Mains transformer Capacitor array at the bottom of the PSU
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Opening the case
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Removing the side covers from the PSU
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TEMPEST PSU with its side panels removed
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TEMPEST PSU interior seen from the right
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PCB inside the PSU
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PSU interior seen from the right
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PSU circuit detail
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Removing the PCB
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Interior of the PSU with the PCB folded away
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The 24V relay that blocks the power output of the data cable is not present
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Dummy-load resistor array
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The five dummy-load driver circuits
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Close-up of the STROBE-sensing circuit
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Russian IC on the PCB
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Mains transformer
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Capacitor array at the bottom of the PSU

References
  1. 2TC613 (KTC613), Datasheet
    Retrieved July 2006.
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Crypto Museum. Created: Monday 12 May 2014. Last changed: Tuesday, 13 June 2017 - 20:46 CET.
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