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Motorola D-1118
Mobile Data Termial

D-1118 is a mobile data terminal, developed by Motorola (USA) in the late 1970s. The terminals were developed especially for use by the police and were mainly built into police patrol vehicles. The unit is commonly known as the D1118-MDT, but is also referred to as the D1118-B [1].

The image on the right shows a typical D1118 terminal as it has been in use with the police force for many years. It is difficult to determine its age as there are no date markings on the device or the PCB, but judging from the data-codes on the various chips, it was built in 1980.

The terminal is housed in a rugged plastic case and features a 5-row dot-matrix plasma display. Below the display is an extended keyboard with the usual QWERTY layout and a row of red keys marked STS-A to E and MSG-A to F. All wiring is connected via a 25-pin sub-D socket at the rear.
D1118-B donated by Barry Wels [1]

Different versions and variants of the D1118-B are known to exist, in particular with different keyboard layouts (see below) and additional – often customer specific – functionality. The variant was probably identified by an extension to the model number. The model shown in the images is identified as the D1118-B SP13. The extention 'SP' probably stands for 'Special'.

Motorola D1118-B terminal Front view of the terminal Close-up of the keyboard Emergency button Close-up of the extended keyboard and the Motorola logo Two switches at the front Switch and rotary knob at the right Dongle inserted at the rear
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Motorola D1118-B terminal
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Front view of the terminal
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Close-up of the keyboard
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Emergency button
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Close-up of the extended keyboard and the Motorola logo
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Two switches at the front
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Switch and rotary knob at the right
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Dongle inserted at the rear

At the bottom left of the keyboard is a red button marked EMR, which stands for EMERGENCY. This key has a rig around it to prevent it from being pressed accidently. The EMR button would be used by a police officer to send a distress signal.

Two slide-switches are present at the front of the terminal. The leftmost one is the power switch, which is used to turn the terminal on and off and the rightmost one is the light switch. Both switches are normally labelled, but with the terminal in the image, the text has come off completely. The light switch is used to illuminate the keyboard in the dark. For this purpose, a light is hidden under the display.

The keyboard has the standard QWERTY layout, with some additional function keys at the top row. The keys are all marked as STS or MSG buttons, but have an additional text printed above them. Please note that these markings differ for the various users and countries. The function keys on the D1118-B SP13 are different from the ones described by [2] . Furthermore, the layout of the small keyboard extension at the right may differ from the one shown here. The function keys are marked as follows:

Key Meaning Description
AVL Available  
EN RT En route  
AT SN At scene  
INC SEC Incident Secure No further assistence needed
OTHER Other message  
WNT PER Wanted Person  
STL VEH Stolen Vehicle  
REG REQ Registration Request Check the licence plate of a car
DR LIC Driver's Licence Check  
INC LIST Incident List Overview of recent incidents
Bottom left:
EMR Emergency Used in case of distress
At the right:
TXT Text  
ACK Acknowledge  
NXT MSG Next Message  
CMP Compare (?)  
STS LN Status Line (?)  
RCL Recal  
CLR Clear  
STO Store  
The D1118-B is very service-friendly and can easily be opened by loosening 6 cross-head screws at the bottom. The two halfs (bottom section and top lid) can be separated without removing the cables. The bottom section contains two PCBs that are stacked on top of each other. The top lid contains the keyboard, the diplay and the display controller.

The top board of the bottom section contains the actual CPU, the memory and the EPROMs with the firmware. The image shows a close-up of the microprocessor and some of the I/O chips. The function of the DIP-switches above the processor is currently unknown.

The upper board is connected to the bottom board by means of a single flatcable at the front. The bottom board contains additional logic and the oscillator. The crystal is socketed on the board and is held in place between the two PCBs with a piece of foam.
CPU and I/O chips

The bottom board also contains the interface to the radio. The data-bits are interleaved as per protocol and the baudrate can be selected by some jumpers, although the exact baudrate is unknown at present. The images below show the interior of the D1118-B in greater detail. The rightmost image shows the character generator, which is mounted to the rear of the display.

In the unit shown here, it is rather difficult to determine which components are used, as most ICs are marked with dedicated Motorola OEM numbers. The processor is marked 61L31. According to [2] it is an Intel 8049, but this remains to be seen, as the chip bears the Motorola logo. Furthermore, Motorola and Intel microcontrolers have significant design differences with respect to address and data busses. The three I/O chips are marked 61L32, which are in fact a Motorola-built SC67314P PIAs.

Interior of the D1118-B Processor board CPU and I/O chips Lamp for keyboard illumination Bottom board DB25 connector and buzzer Removing the crystal from its socket Display controller
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Interior of the D1118-B
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Processor board
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CPU and I/O chips
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Lamp for keyboard illumination
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Bottom board
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DB25 connector and buzzer
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Removing the crystal from its socket
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Display controller

25-way D-type connector
In 1998, a hobbyist [2] managed to find the most important connections on the 25-way D-type connector at the rear of the unit. These comprise the various voltages needed to get the unit going. The following connections are currently known:

  1. GND
  2. PTT (push-to-talk)
  3. DISC (directly from the receiver's discriminator output)
  7. GND
  8. 12V
  9. 5V
  16. 250V
  19. 12V
  21. 5V
  25. GND
So, to get a surplus D1118 unit going, you would need an external power supply unit with +/- 5V, +/- 12V and -250V. The -250V is needed for the plasma display. When building such a power supply, beware that 250V is a dangerous voltage. Furthermore, take care to shield the -250V from the other voltages and signals as it can easily damage the circuitry.

The data protocol used by the D1118 mobile data terminal is currently unknown, but it is likely that it is the same MDT-4800 protocol used by Motorola's other MDTs. It is basically an 4800 baud protocol, that uses 112 bit data packets with bit interleaving and error-correction. It also has clock synchronisation and frame synchronisation packets.

Please note that, apart from a rather complex method of bit-interleaving and error-correcting, most MDTs have little or no encryption at all, although Motorola promised their customers a secure communications system at the time. Because Motorola tried to keep the data protocol secret, this is a typical example of Security by Obscurity.

A full description of the MDT-4800 protocol, complete with the circuit diagram for an interface and suitable C-code, is available from the download section below. Please note that the software is not ours and that the copyright belongs to the various contributors. Please check the text and the source code for their credits.

The Motorola D1118 Mobile Data Terminal was featured in the original Blues Brothers movie. In the movie, the system was called SCMODS, which stands for State County Municipal Offender Data System. In one scene, it shows Elwood's criminal record:

    ILLINOIS LICENSE: B263-1655-2187

  1. Motorola MDT-4800 protocol
  1. Barry Wels, D1118-B - THANKS !
    Device featured on this page kindly donated by Barry Wels.

  2. L0PHT - Heavy Industries, Background information on Motorola Mobile Data Terminals
    Brief description and some ideas on how to get it to work.
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Crypto Museum. Created: Sunday 10 February 2013. Last changed: Saturday, 24 February 2018 - 13:55 CET.
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