BeebMaster - I Want an Econet!
BeebMaster

Econet
Terminators



BBC
Motherboard
Terminator		 Acorn Level 1 Terminator Acorn
Terminator
Box
SJ Research
Terminator
Plug		 SJ Secure
Terminator
Box		 American
Terminator
Box



An Econet network is a line of cable and not a circuit. As such, it has two ends and each end must be fitted with a terminator. This is to prevent the reflection of data and clock signals back across the network once the end has been reached. Terminators provide the necessary circuitry to absorb these reflections to allow the Econet to function without disruption. Although very short networks of two or three stations may work without terminators, they are recommended for all Econets to guarantee reliability.

I hope you will click on the links above to learn more about Econet terminators.



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BBC Motherboard Terminator

The very earliest form of Econet terminator was in fact part of the Econet interface on the BBC motherboard. Up to issue 3, the Econet interface circuitry included the necessary resistors to correctly terminate the network. This meant that a BBC containing the terminator had to be located at one end of the network.


Acorn Level 1 Terminator
This is also known as the powered Terminator Box because it runs off a mains power supply. They have one Econet socket for connecting to a network and require an 8V DC power supply.

There is more information on the Level 1 Terminator here.


Acorn Terminator Box Type 2
Acorn Terminator boxes are similar to socket boxes from the outside except that only one socket is provided.
The terminator box has an identical circuit to the socket boxes. Down the left-hand side of the little board are the words "Econet Box Terminator".
In the case of the terminator box, the right-hand DIN socket is missing and five resistors and a capacitor are soldered at various places.

SJ Research Terminator Plug
The SJ Research terminator comes in the form of a small silver plug which contains the necessary terminating resistors.
The plug is simply attached to the end socket of a network of socket boxes or T-pieces, or it can be mounted inside a secure terminator box. This makes it easier to expand a socket box network as you simply remove the plug and start wiring new boxes beginning at the spare set of connectors inside the last box. With a terminator box, you must first disconnect the box before you can start adding.

SJ Research describe a network scenario where the clock is at the end of the network instead of the middle. In this case, the terminator is plugged into one of the sockets on the clock box. This would not be possible with terminator boxes.

SJ Research Secure Terminator Box
SJ Research Secure Terminator Boxes are a special type of network box which are identified as having no sockets on the front panel.

These boxes have a dual function as either a secure terminator box or a secure connector box.
Inside, the circuit board is very similar to the SJ Research socket box with its two sets of cable connectors. However, there is only one Econet socket inside and this is facing to the right. A cut-out square hole to the right-hand side of the box allows you to see inside the secure box.
There is a layer of backing material underneath the circuit as there is not enough room for a layer of polystyrene because of the orientation of the socket.

As a secure terminator box, the socket takes one of the SJ Research terminator plugs. The idea here is that the terminator is safely housed inside a sealed box preventing any oiks from pulling it out of a socket box and disrupting the network.

As a secure connector box, an Econet lead is connected to the socket for use with a fileserver. The cut-out hole allows the lead to pass outside the box, the intention being that the fileserver's connection to the network is securely kept inside a box.

I think the secure connector box must have been an afterthought on the part of SJ Research since it is really no more secure than plugging a fileserver into any other socket box: just because the socket is not visible doesn't mean the lead cannot be removed!

American Econet Terminator
I did not know about this type of Terminator until August 2003 when, thinking I had got hold of the Acorn Type 1 Terminator at long last, this specimen arrived. There is more about the American type Terminator here.

I believe the above to be a comprehensive survey of all the types of Econet terminator ever produced. If you know otherwise, let me know!



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