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Digital message entry device · DMED - under construction

TMD-326 is a digital message entry device, also known as a burst transmitter or burst encoder, developed in the late 1970s by Tadiran in Israel. The device allows short tactical messages with a maximum length of 16 nine-character groups to be sent at high speed over HF, VHF and UHF radio links, with excellent immunity against noise, jamming and Radio Direction Finding (RDF).

The device can send messages at a speed of 75, 150 or 600 baud, and was inteded for use by air observers, reconaissance units, special forces (SF) and forward artillery. It measures 210 x 105 x 52 mm and weights 1.67 kg, battery included.

The unit is housed in a military green enclosure with connections at the front and controls at the top. Operation is via a rotary selector, a volume knob and a 16-button keypad. Towards the rear is a red 9-digit alphanumeric LED display with a hinged cover to shield it from bright sunlight. A protective green raincoat is available separately.
Tadiran TMD-326

The TMD-326 was commonly used with a manpack radio, such as the AN/PRC-77, or a vehicle set like the AN/VRC-47 (RT-524), in which case it was to the spare U-229 socket (re-transmit) of the radio. It can also be modified for other types of radio sets, such as the BE/GRR-476.

Tadiran TMD-326 with canvas carrying case
Tadiran TMD-326 in canvas carrying case
Tadiran TMD-326
Display cover closed
Connections at the front
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Tadiran TMD-326 with canvas carrying case
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Tadiran TMD-326 in canvas carrying case
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Tadiran TMD-326
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Display cover closed
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Connections at the front
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Protective carrying pouch CW-326
Digital Message Entry Device TDM-326
Interface box IB-326
U-229 audio cable
Cable for auxiliary equipment
Pouch   CW-326
The TMD-326 can be fitted inside the green carrying pouch shown in the image on the right. It can be attached to a soldier's webbing and protects the keyboard and display.

The pouch has a flap at the top that covers the controls, and is held in place withg Velcro strips.
Tadiran TMD-326 with canvas carrying case

Message device   TDM-326
This is the actual TMED device, which is fully self-contained. It is powered by an internal 7.2V NiCd battery that is installed at the bottom, just below the display.

At the front is an U-229 socket – for connection to a radio set – and a 14-pin female socket for connection of auxiliary equipment, such as the IB-326 interface box.
Tadiran TMD-326

Interface box   IB-326
Messages from the TMD-326 can be printed directly on a teleprinter (telex) by using the IB-326 interface box shown in the image on the right. The box is connected to the AUX connector of the TMD-326 by means of a CX-326C cable, whilst the teleprinter should be connected to the ADo-8 socket at the rear.   
IB-326 interface box

Audio cable   CX-326/A

AUX cable   CX-326/C

  • Message
    Up to 16 nine-character groups (sentences)
  • Modulation
    Frequency Shift Keying (FSK) using internal modem
  • Baudrate
    75, 150 and 600 baud (bits per second)
  • Bit error
    5·10-4 at 12dB S/N
  • Audio out
    1.4 mV into 150Ω load
  • Audio in
    0.1 to 3V from radio set
  • Display
    9-digit alphanumeric
  • Power
    7.2V DC NiCd battery
  • Current
    420 mA in operations (100 mA with display off)
  • Temperature
    -40°C to +55°C
  • Dimensions
    210 x 1-5 x 52 mm
  • Weight
    1.67 kg with battery
  • 6T-133
    Rechargeable 7.2V NiCd battery
  • TMD-330
  • CW-326
    Carrying pouch
  • IB-326
    Interface Box
  • TMD-328
    Power Supply Unit
  • CX-326/A
    Audio cable to radio set
  • CX-326/C
    Auxiliary cable (for IB-326 interface box)
  • CX-326/D
    Power cable
  1. Digital Message Entry Device TMD-326, Operator Manual
    OM 193B / 3609504. Tadiran, August 1979.

  2. Interface Box IB-326, Operator Manual
    OM 2336-09525-00. Tadiran, July 1983.
Further information
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Crypto Museum. Created: Sunday 16 June 2019. Last changed: Saturday, 26 October 2019 - 08:19 CET.
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