BeebMaster - I Want an Econet! - Build your own Econet

Build your own Econet

Setting up the Network

The network must be correctly installed before it can be used. Full information and practical help is given here to get you started but more detailed instructions, particularly for larger or more complexly laid out networks, are given in the Acorn Econet Installation Guide and SJ Research Installation Instructions which are available from the BBC Documentation Project. The Econet Design and Installation Guide is very comprehensive, if you can get hold of it, as it covers Acorn and SJ Research parts and machines from the BBC Model B to the Acorn A5000.

Required Components

At least two BBC Micros

A network is set of computers connected together with the ability to communicate with each other and retrieve data from a shared storage facility, the file server. You will need at least two Beebs and, as it is likely that one of them will become the file server, three or more is recommended if you want to be able to NOTIFY and REMOTE other stations.

Practically all Acorn machines ever produced can support Econet, even the Acorn System range, Atom and Electron as well as the 32-bit machines.

I am sticking to Beebs here as far as possible for simplicity although much will apply to non-Beeb Acorns.

Econet interfaces in each machine

In the case of the BBC Model B, this is an upgrade to the top-left hand section of the main circuit board. Econet Upgrade Kits can be purchased from my BeebShop.

In the Master Series, the Econet interface is a small module which plugs directly into the main motherboard just in front of the Econet port. I have had a limited number of Econet Modules specially manufactured, so if you can't find them anywhere else, buy them here.

Network Filing System ROM in each machine

The BBC Model B generally takes the Network Filing System (NFS). This is either an 8K ROM containing NFS 3.34 or NFS 3.40 or it is contained in the DNFS ROM as NFS 3.60. There is also a BBC B version of the later Advanced Network Filing System, version number 4.18.

For the Master Series, the Advanced Network Filing System is needed. This is a 16K ROM and the last version is ANFS 4.25.

If you are stuck for a ROM, I sell various different types at the BeebShop here.

An Econet Clock

Each Econet requires one - and only one - Econet Clock. Its purpose is to regulate the transmission of data around the network. Without it, Econet cannot function. Some people have built their own clocks based on the simple circuitry in the Level 1 type clock, but if you want a proper, brand-new Network clock, the BeebMaster Econet Clock is available here.

Econet Leads

These are 180-degree 5-pin DIN to 180-degree 5-pin DIN leads, usually in black or grey. They connect from each computer to the main network cable line via socket boxes. You will need one Econet lead for every machine and two more leads for the Clock.

If you fancy a bit of soldering, you can make up some leads using suitable cable and 5-pin DIN plugs. Alternatively I have a stock of new Econet leads at the BeebShop.

Socket Boxes or T-Pieces

Socket Boxes provide outlets along the network cable line for stations and the Clock to be connected.

Each socket box has two sockets. You will need a socket for each machine and two further sockets for the Clock. If you are going to use terminator plugs, two further sockets will be required for the plugs.

As an alternative, T-pieces can be used. These are T-shaped junction pieces providing three sockets. They are connected together with Econet leads so if you use T-pieces, a lot more Econet leads will be needed. The T-pieces are linked at the two-socket end with the leads, leaving the remaining socket free for stations and the Clock.

There is more information on the various types of socket box and T-piece here.

Two Terminators

Terminators, which are small circuits containing terminating resistors, must be fitted at each end of an Econet network. The purpose is to absorb any data signals reaching the end of the network which might otherwise be reflected back up the cable and disrupt the network.

Terminators take a number of forms. They may be passive boxes made by Acorn or SJ Research which are wired into the end of the network as if they were another socket box. Early Acorn Terminators are mains powered and plug into the end socket at each extreme of the network. They may be in the form of small silver plugs which either plug into the end sockets of the network or are mounted inside an SJ Research secure terminator box.

There is more information on the different forms of terminator here.

It may be possible to run a small Econet of two or three stations and short total cable length without terminators. However, I wouldn't recommend this as it is likely that the network stations will behave unreliably. If you can't get hold of any terminators, then Acorn socket boxes can be altered to function as terminators by making the following modifications:

1.Remove the right-most DIN socket.
2.Add a 56 ohm resistor to position R1.
3.Add a 56 ohm resistor to position R2.
4.Add a 1K ohm resistor to position R3.
5.Add a 220 ohm resistor to position R4.
6.Add a 1K ohm resistor to position R5.
7.Add a 10uF Tantalum capacitor to position C1.

Network Cable

Whereas T-pieces are connected together with standard Econet leads, socket boxes are wired together using suitable cable. You will need cable with five wires inside it. The cheapest way to get this is to buy cable known as "4-core with shield". This has four separate insulated wires surrounded by non-insulated wire which you twist together to make the fifth wire. People often use Cat5 cable as an alternative, presumably because they have a supply of it lying around at home. It will work fine but you do end up wasting the unused wires inside.