BT Merlin M2105

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Introduction

The BT Merlin M2105 was a dedicated communications terminal which was designed and manufactured for BT by Acorn. It is an Electron with an expansion box containing, modem, voice synthesis, serial and parallel ports. which connect to the Electron via the expansion interface at the back of the Electron. These were supplied by BT to various customers, mainly unknown, but including Interflora to allow dial-up point to point messageing, in the days before email and instant messaging.

Manuals and documentation

None.

The Acorn Electron World has a good review of the Acorn Merlin M2105 Comms Terminal 

British Telecom M2015

In 2006 I bought an M2105 on ebay, here are some pictures:

BT Merlin M2105 in its box

  The BT Merlin M2105 in the bottom half of the polystyrene packaging. Unfortunately there were no manuals or instructions.

BT Merlin M2105 switched on with Microvitec monitor

  Unfortunately when the M2105 is switched on it hangs waiting on a printer (see screen). Since I didn't have a suitable printer available, I could get it to go any further. There seems to be no way to breakout the the Electron MOS.

BT Merlin M2105, an Electron with an expansion box

The M2105 as it comes out of the box. The Electron is connected to the Expansion box using the expansion bus interface and the 2 parts are held firmly together. Both boxes have labels missing, the Electron above the keyboard and the expansion box immediately after the connection.

BT Merlin M2105 right side

The right side of the M2105 showing the connection for the 19V AC power supply.

 BT Merlin M2105 back

  The back of the M2105 showing the BT Merlin label, Also vivible are the lead from the modem, parallel printer socket and a serial port.

BT Merlin M2105 left side 

The left side of the M2105 shows the Electron ports, from left to right: TV, Video, RGB and cassette. I have only used the RGB port to connect a colour monitor. I am not sure how you could use the cassette port since you can't break out of the Merlin application to BASIC.

BT Merlin M2105 bottom

The bottom of the M2105 showing the Acorn Electron label. There is a large indent to the back of the expansion unit where another label could have been.

BT Merlin M2105 Expansion bus connector

M2105 expansion box showing the connector to the Electron expansion bus.

BT Merlin M2105 Electron Expansion bus

The back of the Electron showing the expansion bus, exactly the same as for a Plus 1 or Plus 3.

BT Merlin M2105 Electron open

On opening the M2105 Electron, you can see that it has the same motherboard as the normal Electron (p/n 205,000 Iss. 4). But you can immediately see 2 differneces with the standard Electron, there are two small daughter boards - one where the keyboard collects to the motherboard and the other by the expansion bus. I don't know what they do.

BT Merlin M2105 Electron motherboard

 The M2105 Electron motherboard with the keyboard cable removed showing, from Left to right and front to back:

• The 4 ports on the left, Cassette, RGB, Video and TV,
• The daughter board with the cable connector,
• The big chip in the middle is the 6502 CPU
• The Ferranti ULA under the metal cover
• The daughter board by the expansion bus.

A His-Res verion of this picture is available HERE .

BT Merlin M2105 expansion box open

  M2105 Expansion board clearly marked Acorn Computer Business Division M2105 0221,000 Issue 5. The board shows, from left to right and front to back:

• 4 x 8K RAM chips at the front left hand side,
• 3 x 16K EPROMs with the labels torn off, above the RAM,
• 1 x SCN2681A DUART at top which suggests the unknown port is a 25pin D serial port,
• The TMS6100 and TMS5220 speech synthesis chips are on the bottom right above the speaker,
• The modem is in the top right below the telephone cable,
• The Parallel port is driven by a 6522 below it ,

A hi-Res version of this picture is available HERE .

Specification: