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The image on the right shows the burst encoder as it is shown in the
technical manual [A]. The device measures 190 x 72 x 50 mm and weights
1.40 kg. It has the same length as the receiver and the
accessory box, but is 3 cm less wide.
The device is connected to the transmitter by means of a short cable with
a rectangular 6-pin plug at either side. The recorder is powered via this
cable and delivers its modulated signal to the transmitter when in playback
mode.
The device is only suitable for (pre-coded) numerical messages consisting
of the digits 0-9. The numbers are recorded onto a magnetic tape.
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Once the message is recorded and the transmitter is tuned to the desired
frequency, the message can be played back at high speed by pressing the
REPLAYING button at the top left.
It takes just 15 seconds to send a message of 200 groups of 5-digits each,
which greatly reduces the risk of interception and radio direction finding.
When playing back, the signal from the pickup head is amplified
and sent to the transmitter, where it toggles the main oscillator in order
to produce CW.
A later variant of DÁVAČ is
MEŠIC
(moon) which was supplied
with the SIRIUS III radio station.
It is nearly identical to the DÁVAČ, but has
its endless tape located at the top. Furthermore, it features a different
keypad and has a different socket for connection to the SIRIUS III transmitter.
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DÁVAČ is the Czech word for 'keyer'.
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Správa 6 refers to Government Department 6: Communication Technology.
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Operation of the device is pretty straightforward. After connecting it to
the transmitter (via the 6-pin socket at the right side), it can be switched
ON by sliding the ON/OFF switch to the right. First, the tape should be fully
ereased by pressing the ERASE-button. The tape will then run for approx. 15
seconds during which time a Direct Current (DC) is supplied to the recording
head.
Once the tape is ereased, a new message can be recorded. Press the START
button to initiate a recording session. Each time one of the number-buttons
is pressed, the tape is advanced and a rotating drum with interrupt switches
causes the selected number to be recorded on tape as a series of dashes and
dots (morse code). When the message is complete, the STOP button should
be pressed. Now set the transmitter to the desired frequency and press
the REPLAYING-button.
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The interior of the DÁVAČ can be accessed by removing the 6 screws
around the edges of the control panel. The entire assembly may then be
removed from the case. The device is built around a metal chassis with
the motor and the coded drum taking up one half, and the electronics
taking up the other half. The tape mechanism
is located at one of the short sides.
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The image on the right is taken from the manual and shows the device
as seen from the bottom. At the upper right is the DC electromotor that
drives the mechanics. Immediately below that is the coded drum that consists
of 10 discs of which the notches represent the dashes and dots that make up
the morse code characters 0-9.
At the far left is the actual recording mechanism that can be accessed from
the short side of the device.
It consists of an endless magnetic tape that is held in a small compartment,
a pressure roller, a capstan, a record/playback head and several tape guides,
much like an old recorder.
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As far as we know, there are no surviving examples
of this device, which is why we can only show the black-and-white
photographs from the manual here. The device is very similar to the
later MĚSIC burst encoder
however, so for a closer look at the
mechanism, please follow this link.
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DÁVAČ should be connected to the
SIRIUS transmitter (TI-466 AB)
via the rectangular 6-pin socket at the right side. This socket is
identical to the one at the front of the transmitter. As the burst encoder
should be placed in front of the transmitter, only a short 1:1 cable is
needed.
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- Modulation (+)
- LT (6.3V AC)
- LT (6.3V AC)
- HT in
- HT out
- Modulation (GND)
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- TI-485
- DAVAC
- DÁVAČ
- SIRIUS D
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© Crypto Museum. Created: Tuesday 04 August 2015. Last changed: Saturday, 14 November 2020 - 10:32 CET.
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![DAVAC burst encoder. Photograph via [2].](img/davac_10t.jpg "image # davac_10.jpg")
![DAVAC burst encoder. Photograph via [2].](img/davac_10.jpg)
