BSB DMAC receivers and modifications

Receiver DataVision (data port) AGB Audience Survey D2MAC mod? Notes
Ferguson SRB1 :?: Modified for D2MAC and PAL reception by Trac Satellite and others.
Tatung TRX2801
(Decca DRX-2851)
:?: Data port is present but used for AGB Audience Survey. DataVision not expected to be implemented.
Philips STU902 :?: Manual suggests that the data port “may be used for features such as an Audience Survey”
Modified for D2MAC by Transworld Satellites.
ITT-Nokia/Salora 5903 :?: :?: :?:

DataVision support is speculative - it's not known whether this was actually deployed by BSB. An article in New Scientist from January 1990 (BSB faces setback over business data service) says that Ferguson “had been burning midnight oil to write the software needed to decode Datavision, and [believed] it was ahead of its three competitors, Philips, Salora and Tatung.”

A BSB Datavision promo video is available on Youtube.

There are several versions of the ITT DMA2285 DMAC/D2MAC decoder.

According to an article in Maplin 'Electronics' magazine, March 1993, widescreen and soft-scramble will only work on chipset version 30 and later.

Ferguson documentation:

The SRB1 was the 'standard' BSB receiver at launch, and proved to be very versatile. After BSB's closure, many of these were sold at a low price as liquidated stock and modified to receive other satellite signals. Trac Satellite were a key player in this market, producing several modification kits ranging from a simple D2MAC FTA ROM-swap to a full dual-mode PAL/D2MAC conversion with a Eurocrypt smartcard slot and built-in “two-chip” Multimac smartcard.

I don't know what the difference between the various Trac Satellite ROMs is, or how to identify the modifications. If you know, please drop me an email:

Hidden screens

Pressing Setup on the back panel of the receiver will display the ROM version number.

Pressing Shift then Menu will display the channel information: channel number, frequency, channel name (from the SI data), audio type, and bit error rate.

RGB/LO tuning

Press Menu to open the on-screen setup menu. Hold Shift and press 9 on the remote.

  • Press Enter to switch to Decoder mode
  • Press Cancel to switch to Receiver mode
  • 1/4, 2/5, 3/6 adjust the RGB cutoffs.
  • 8/9 adjusts the local oscillator
  • 0 stores the new settings, VIEW exits without saving

Temporarily reverting the PAL/DMAC mod

The PAL/DMAC modification can be partially reverted to allow the original Ferguson firmware to be used. This can be useful to read out the ACM data on a modified Ferguson receiver.

This is a somewhat involved process and not for the faint of heart.

  1. Unplug the MAC board from the card reader board. Plug the MAC board directly into the receiver motherboard.
  2. Desolder the left and right audio wires going from the MAC board to the PAL board.
  3. Disconnect “VBC” and “VI” from the PAL board. Connect them together.
  4. On the underside of the PCB, a diode and a wire are connected to the centre pin of transistor TV19. Desolder the diode and insulate the end of the wire.
  5. Follow the service manual guide to set up VCO levels and RGB cutoff.

Beware that the insulation on the wire used by Trac has a tendency of melting easily. You may need to repair wires with splices and/or heatshrink to reinstall the mod.

LNB types

The Trac ROMs support three types of LNB:

Type LO offset Frequency range
FSS 10.0 GHz 10.9 to 11.7 GHz
BSB DBS 10.75 GHz 11.7 to 12.5 GHz
Telecom 11.0 GHz 11.95 to 12.75 GHz

The above assumes a receiver tuner range of 0.95 to 1.75 GHz.

DATA port enhancements

The Trac D2MAC/PAL modification adds a 0V/12V switchable output and a PAL video signal to the DATA port.

The DATA port is an 8-pin DIN socket.

DATA port pin Function
1 Ferguson: Data output
Trac: “VO”: +12V / 0V switchable – NOTE outputs -11V in “0V” mode
2 Ground
3 Ferguson: NC
Trac: Always-on PAL video to decoder. 1V p-p on approx. 3V DC level
5 Ferguson: NC
Trac: “DI”: Decoder video input

The video pins can be connected to a SVA-1 Videocrypt decoder's Decoder SCART port. The de-emphasis filter needs to be enabled if HackTV is being run with the “--filter” option.

Tatung documentation:

I've created a LIRC IR remote configuration file for the TRX-2801:

To enter Test mode:

  1. Hold the TEST key on the local keypad while powering the receiver on.
  2. Keep the TEST key depressed until the LED display shows H (standby).
  3. Press the Standby button to wake the receiver. The receiver will display scrambled pictures when not authorised, instead of blanking the video – this is intentional.
  4. Press MENU to display the main menu.
  5. Press 6 to enter the Test menu.

The receiver will remain in test mode until it is switched off and back on again.

ACM diagnostics – press Menu, then the 0 (zero) key.

Transworld Satellites made several D2MAC modifications for the STU902. These ranged from an EPROM-only mod which only allowed access to free-to-air channels, right up to a Eurocrypt-capable D2MAC mod with a front-panel card-slot.

I'm looking for information and instructions for the Transworld mods, as I currently have a Transworld-modified receiver which powers on, displays “00” then “01” on the display, but otherwise doesn't work. If you have any details on these upgrades (or others), please contact me by email.

The main CPU is a Philips 80C31, running at 11.0592MHz.

The PSEN (program store) is connected to the 27C512 program memory EPROM.

The XDATA (external data) memory is mapped as follows:

  • 0000 to 1FFF: MK48H64 RAM “7501”, not battery backed. 8 Kbytes.
  • 2000 to 7FFF: RAM shadow copies (undefined)
  • 8000 to FFFF: Subdecoded by 74F139 “7512”:
    • 8000 to 9FFF: Display Segment Latch “7514”
      • Bit 0: G
      • Bit 1: F
      • Bit 2: E
      • Bit 3: D
      • Bit 4: Red and Green LEDs (Red = DIG1, Green = DIG2)
      • Bit 5: A
      • Bit 6: B
      • Bit 7: C
    • A000 to BFFF: Display Common, Switches and Control Latch
      • Bit 7: → C7
      • Bit 6: Digit 1 / Red LED
      • Bit 5: Digit 2 / Green LED
      • Bit 4: STDBY → D6
      • Bit 3: RESET ⇒ B4, C5
      • Bit 2: Standby switch, 0 to sense on P1.3.
      • Bit 1: Service link, 0 to sense on P1.3.
      • Bit 0: Setup switch, 0 to sense on P1.3.
    • C000 to DFFF: IMBUS Register Read
    • E000 to FFFF: Access Control Module
      • A11: Register Select
      • A12: Read/!Write


  • INT0: Infrared remote
  • INT1: Access Control Module
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  • Last modified: 2023/01/30 23:32
  • by philpem