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← Tadiran Voice
Voice and data crypto unit
The SEC-15 was a voice and data crypto system developed in the early 1980s
by Tadiran in Israel.
It was intended for use in combination with existing radio networks, such
as Clansman and
the American VRC radios.
It was built according to specifications layed out by the
IDF (Israel Defense Forces), but was also used by the US Army and
a number of NATO countries.
Due to its shape and connector at the rear, the unit fits in the same space
as the R-442 receiver.
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The image on the right shows a typical SEC-15 crypto unit.
It is housed in the same case as the earlier SEC-13
and the R-442 receiver, making it easier to add it to an existing setup.
It has the common 18-pin connector at the back.
Rather than lamps, LEDs are used on the front panel. At the top are LEDs
for TRANSMIT, ALARM and RECEIVE. Immediately below that, is the crypto
selector with a red (CLEAR) and green (SECURE) LED.
To the right of that is the selector for the MODE of operation.
It is also used for entering and erasing the current key settings.
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Below the CRYPTO and MODE selectors is a door that gives access to some
additional controls. Behind the door is a selector for the current key (0-9),
an ERASE button (used when the MODE-selector is set to ERASE) and
baudrate settings for the terminal and data connection. Using the table
on the inside of the door, the baudrate can be set between 50 and 2400 baud.
A switch allows selection between ASCII (7-bit) and
BAUDOT (5-bit)
encoding.
At the bottom of the front panel are two large military connectors.
One is used for connecting the SEC-15 to a (radio) modem, whilst the other one
allows the connection of a (TTY) terminal.
At present, no further information about this crypto unit is known.
It is possible that it was the successor to the SEC-13
but it is also possible that it was aimed at a different application
as it supports both voice and data.
It is clear that they were scheduled to be replaced from 1995 onwards
by more modern equipment such as the
SINCGARS radios.
Nevertheless, they were in service well into the 2000s.
Although they were used until recently, they sometimes show up on the
European surplus market, which is also were the device shown here was found.
If you have additional information about any of the Tadiran crypto devices,
please contact us.
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The interior of the SEC-15 is easily accessible and gives a lot of information
about the state-of-technology when the unit was developed. It also tells us
approximately when the unit was built. After removing the 6 bolts from the
top lid, the interior is revealed.
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The unit consists of 7 printed circuit boards (PCBs), numbered 1 thru 7,
an enclosed A6 PRO module and a series of
power supply units (PSU). The PCBs are all slotted into a so-called
backplane that resides at the bottom of the unit.
The main connector, the front panel and PSU are all connected to the backplane.
Each of the PCBs can be removed, by tilting the white levers and lifting
the PCB out of its bay. Each PCB has an index key mounted to its main
connector, to prevent it from being inserted into the wrong slot.
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The manufacturing dates on the electronic components inside the SEC-15 vary
between 1980 and 1983. This suggests that the unit was developed and built in
the early 1980s. As the design and finishing of the PCBs is more professional
than those of the SEC-13 it was probably released somewhat
later. This is also supported by the fact that LEDs were used instead of lamps.
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Hi-res photographs of each of the 7 PCBs are available in the second row of
images above. Most of the PCBs carry analog circuits and interfacing beween
the analog and digital parts (I/O). The first PCB (A1) contains the memory,
whilst A2 carries the processor (CPU). According to text on the PCBs,
the function of each board is:
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- Memory
- CPU
- Communication
- I/O Card
- Interface
- Modem
- Cipher
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The SEC-15 is built around an AMD 8085 processor that is located on the
second PCB (A2), together with a 4.096MHz crystal and some glue logic.
Unlike the SEC-13, the ROM and RAM memory of the
SEC-15 is located on a separate PCB (A1).
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Like the SEC-13, 256 bytes of battery-backed RAM are available for the
storage of key material.
Furthermore, the A1 board contains 5 Mostek MKB4118 static RAM ICs,
delivering a total of 5KB of RAM, giving much more flexibility than
with the SEC-13.
The firmware is stored in 3 AMD 2732 EPROMs.
The 8085 processor was developed by Intel in 1977 and was based on the
earlier 8080. It has an 8-bit databus and a 16-bit address bus, of which
the lower 8 bits are multiplexed with the databus.
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The images below show the A1 and A2 boards in more detail.
The A1 board normally contains a backup battery in order to retain
the key material in the 256 bytes of battery-backed RAM.
Unfortunately, this battery is missing from the SEC-15 unit shown here.
The rightmost two images below show the space where the battery would normally
reside. The rightmost image shows one set (of 2) of the battery terminals.
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The form factor and shape of the SEC-15 case,
and the main connector at the rear,
are identical to those of the R-442 auxiliary receiver.
This suggests that the SEC-15 could
be slotted into a standard American VRC rack mount.
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The image on the right shows the typical 18-pin connector that is available
at the rear of the unit (here seen from the bottom).
At present, the layout of this connector is unknown to us.
Check the images below for further details of this connector.
The rightmost one shows the solder-side of the connector, seen from the
interior of the SEC-13.
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© Crypto Museum. Created: Saturday 22 May 2010. Last changed: Saturday, 24 February 2018 - 21:01 CET.
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