Econet Network Installation Instructions

Including installation Instructions for:
Twin Socket Boxes
Secure Terminator Boxes
Split Socket Box
Clock Installation Kit
Transient Suppressor Kit

issue 2.04
June 1992

SJ
RESEARCH

SJ RESEARCH LIMITED
J1 THE PADDOCKS
347 CHERRY HINTON ROAD
CAMBRIDGE CB1 4DH
TELEPHONE 0223 416715
FAX 0223 416440

© SJ Research Limited, 1992

While every effort has been made to ensure the accuracy of this document, the descriptions and specifications may be changed without notice. Whilst copyright in this document is reserved by SJ Research Limited on this document, purchasers of SJ Research Econet installation products are permitted to make any number of copies foe their own non-commercial use. provided this copyright notice appears on all such copies.

Disclaimer

While every care has been taken in the preparation of this manual we assume no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein.

All goods and services provided by SJ Research Limited are subject to the company’s terms and Conditions of Sale. A copy of such terms is available on request and such standard terms shall apply on and from the date of actual commencement of such service or the provision of goods.

Econet is a registered Trademark of Acorn Computers Ltd.
All other trademarks are acknowledged _________

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Contents

Introduction ………………………………………………...	2        
Installing the Network………………………………………	2
Network Components
Twin Socket Boxes……………………………………….	7          
Secure Terminator Boxes………………………………...	7      
Split Socket Boxes……………………………………….	8          
Transient Suppressor Boxes ..……………………………	9
Econet Network Cable……………………………………	11         
Application Notes
Econet Network Topology………………………………..	12
Tools for Econet installation……………………………...	14
Laying—in Econet cable…………………………………	14 

Introduction
The packing list for each of the products covered by these instructions appears on the box label for that product. In each ease, the component box comprises a box back, box front, circuit board and polystyrene packing piece (Tufnol® insulator in the case of Secure Terminator Boxes). Secure Term Boxes need to be fixed to their mourning surface with a wood screw with a low-profile head; suitable screws are provided with the terminator boxes. All other products are supplied without fixing screws; we recommend these boxes are secured using No.6 or No.8 dome-head screws.

Each box back is provided with two screw holes to attach it to the mounting surface and a slot for rear cable entries. The boxes can be easily cut or filed to provide alternative cable mounts. The Internal components for each item are mounted on the printed circuit board; in all cases, this board Insulation Displacement Connectors (IDCs) for connection of the main Econet cable. This means of connection saves stripping or soldering of the main cable, allowing easy installation without the need for electrical power, while giving a connection of very high quality. To maintain the quality of installation, it is very important to avoid cutting the Econet cable at the socket locations (except at Split Socket Boxes), as far as it is possible to do so. This also has the advantage that if a wire becomes detached in one socket box the remainder of the network is unaffected. However, each item (except split socket boxes) is provided with two pairs of IDCs to facilitate cable joints where tweaks in the Econet cable are unavoidable (e.g. where joining cable from two reels).

In addition to the components covered by this manual, your Econet network will require suitable cable (see information in the Network Components section), an Econet Clock and Terminators. SJ Research supplies Clock and Terminators as a set (product code CLTSE03); the instruction booklet supplied with this covers setting the network clock rate.

Installing the Network

You are advised to read through these instructions and to consider the Application Notes, at the end of this manual before starting work on Installing your Econet. If you ore installing a number of boxes we strongly recommend use of the tools described on page 14.

1. Plan your Econet installation, deciding on the position of each socket box. Remember that you will need to allow a socket at each end of the network to take the network terminators: you may wish to install Secure Terminator Boxes in these positions. You will also need to provide for installing the Econet Clock - a Split Socket Box is recommended at this position. Decide whether your system requires Transient Suppressors, and if so, where they are to he installed. Finally, remember that it’s easier to provide “spare” sockets when you first install the network than It is to add additional sockets later.

2.	Remove the lid, printed circuit board and piece of polystyrene foam (or insulator) from each of the boxes, and secure the boxes to their mounting surface, using wall plugs as necessary (see the notes on screw types and sizes in the Introduction, above). Mark the

position of the cable entry slot onto the mounting surface and remove the box. Some installers prefer to use adhesive pads for securing the boxes; on a good surface these can be perfectly adequate. In this cue it is better to hold the boxes in place while marking the cable slot positions, since the pads do not allow the box to be removed easily.

3.	If possible, cut a slot in the mounting surface to coincide with the slot in the back of the box. If this is not possible, drill a hole of at least 9mm (3/8”) diameter at either end of the slot. (Alternative cabling strategies are mentioned in the Application Notes.)

4.	Lay in the network cable. If the clock box is being installed at one end of the network then you will need to lay in cable for the entire length of the network; otherwise, run from the clock position to one end of the network. Do not cut the cable from its cable drum at this stage. If you have been able to cut cable slots in the mounting surface simply run the cable for its entire length, and then pull out a loop of cable at each socket position. If you have had to make two holes at each box position then you will need to feed the cable out through one hole and back in through the second hole each time. In this case, installation is eased if you leave a rather larger working loop of cable at each socket position. It is of the utmost importance that you avoid cutting the cable at the socket positions as far as it is possible to do so. Networks with few cable cuts/joins, tested correctly on installation, will invariably work reliably and continue to do so.

5.	Stan installing the boxes from the end of the cable. Remove the outer PVC sheath and the foil (or braided) screen for about l00mm (4”), taking great care to avoid damaging the uninsulated drain core. If you are using a cable in which one colour is repeated (e.g. BICC or RS types), ascertain the twisting, since the correct core will be Identified by the other colour of the twisted pair. Feed the cable through the cable slot in the back of the box, and secure the box to the mounting surface. Place the piece of polystyrene foam (or insulator) into the box. The cut-away portions allow this item to fit between the cable entry points. Insert the printed circuit board and press into place.

6.	Lay each coloured core of the cable into an appropriate IDC slot. Fig. 2 shows the usual way of doing this when the cable is passing through the box; however, on all components except Split Socket Boxes the two connector slots labelled similary (e.g. the two slots marked D+) are equivalent and can be regarded as alternative. Fig. 1 gives the most common colour codings for Econet cables.

Signal	BICC/ RS
Cable	SJ Research
Cable	
Data +	*White	Green	
Data -	Orange	Red	
Clock +	*White	Yellow	
Clock -	Blue	Blue	
Figure 1. Econet Cable: Colour Code 1
The ground (earth) connection is always provided by the drain wire
**The white cores may be “traced” in the colour of the core that they are twisted with

Check that the drain wire is not tangled with the other cores and lay it carefully in place.

Figure 2. Socket Box with cable laid into and around terminal blocks

Position the white insertion tool (or the professional installation tool) over one core of the cable and heal the tool firmly into the slot until the core lies at the bottom of the slot. Note that the tool will only fit in one way round try it in an empty terminal if in doubt, and never force it. Fig. 3 shows the tool and the terminal block, indicating their collect orientation.

Figure 3. Correct orientation of Insertion Tool

Connect the other cores of the cable in the same way. Once the coloured cores have been connected, secure the earth wire in the same way. Take particular care to avoid damaging the earth wire, and note how it is usually passed through the slots in two of the IDC blocks. Do not connect anything to the separate earth terminal of Transient Suppressors at this stage (see notes on Transient Suppressors Kits).

In the first socket box, and anywhere else where a break in the cable is unavoidable, trim off excess cable from the ends leaving about 3mm (1/8”) protruding. Check that the uninsulated drain (earth) wire is undamaged and is clear of all other connections.

On boxes which use the polystyrene packing piece, some installers prefer to leave out this piece until after they have used the tool to push the wires into the IDC blocks. The

polystyrene is then inserted behind the circuit hoard. This approach provides a firmer surface for pushing against when installing the cables; however, you must leave enough slack in the cable to allow you to insert the packing piece after connection.

Important warning: Cables should he installed into the IDC blocks at room temperature; working at low temperatures can damage the connections. Avoid making these connections in adverse conditions. However, once the connections have been made they will not he affected by the cold.

On components other than Secure Terminator Boxes and Transient Suppressor Boxes place the lid on the box, making sure that the DIN sockets align in the holes in the lid, and secure it with the four No.4  self-tapping screws provided.

At this point you are strongly advised to insert a Test Plug as shown in Fig. 4 (below) in this first socket box. In conjunction with a simple multimeter, this will enable you to lest the correct installation of each socket as you install it; time spent on testing at this stage will be repaid in the reliable working of the network over years to come.

Figure 4. Econet Socket “pin-out” and Econet Test Plug

In making these tests, it is essential that Terminators are not installed before the resistance tests are completed.
If yow installation includes Transient Suppressors then particular care needs to be taken when using the multimeter to measure the test plug resistance values. You need to appreciate that a multimeter measures resistance’s by applying a low voltage to the component under test. Thus one lead from the multimeter can be regarded as carrying a positive voltage, and the other as carrying a negative voltage. It is essential that the positive voltage is always applied to the Earth core of the Econet (pin 2 of the Econet sockets). Seemingly illogically, the black terminal/ lead of the multimeter carries the positive voltage and it is this lead which should be applied to the earth pin (pin 2) of the Econet sockets. [If the leads are connected the other way round then the transient suppressor diodes will conduct, causing false resistance values to be given..]

7.	Work beck from the end position to connect up the remaining boxes. At each box position, start by pulling back any slack cable from the portion of the network already

installed. If you are installing a split socket box, or have reached the end of (this branch of) the network then cut the cable at this point. Strip the outer cable insulation, feed the cable through the cable slot in the box, secure the box to the mounting surface and insert the polystyrene packing piece (or insulator) and circuit board into the box. Before installing the cable into the IDCs, push any surplus cable into the cavity behind the mounting surface (if possible).

Assuming you are testing your installation as you go with the test plug referred to above, measure the resistance between the earth pin (pin 2) and each of the other pins in turn: check that each reading you obtain matches the value of the corresponding resistor on the test plug. (As you move away from the end of the network the readings you obtain will increase slightly, due to the resistance of the cores of the Econet cable. The increase should be the same on each pin.) On Twin Socket Boxes always check both sockets in the socket box, in case of faults on the socket box circuit board; on Transient Suppressor Boxes and Secure Terminator Boxes check the resistance’s by pushing the multimeter probes against the metal blades of the IDCs.

On twin socket boxes, fit the cover on the box as described at stage 6. 

Where you have installed a Split Socket Box, plug the short lead from the side of the socket box you have not wired up into the DIN socket on the side you have connected.
Now test the resistance readings on the second socket. If the Split Socket Box is part-way along an arm of the network then install the free end of the network cable into the second set of IDC blocks, and fit the lid to the box.

8.	If the clock is being installed away from the centre of the network, repeat the installation process for the second arm of the network. Install the box at the far end of the network first; as soon as it is installed, move the test plug into this socket.

9.	When all network wiring has been installed and the resistance tests completed, connect the earth terminals on any Transient Suppresser Boxes to the mains earth point (see the notes on Transient Suppressor Boxes). Plug the terminators inside the Secure Terminator Boxes. Replace the lids on these boxes. Connect the clock to the network and test the performance of the net. Ideally you should test that a machine plugged into any socket on the network can communicate with a machine plugged into any other socket. In practice, a minimum test should be to check that machines at opposite ends of the network can communicate with each other. With BBC Master computers this can be done by trying to *View the screen the computer at the opposite end of the network (preferably with both machines in screen MODE 0). With Archimedes computers you can use the Notify option from the icon bar menu, although this is a less rigorous teat. In both cases, make sure the “target” machine is not PROTected. These tests are described in more detail in the instruction booklet for the Econet Clock and Terminator Set copies of this can be obtained from the Technical Support Desk at SJ Research.

Notes:
a.	If it is necessary to cut the cable, or if you are joining two lengths of cable, connect up each end as described in sections 5 and 6 above. Note that each line (Clock+, Clock-, Data+. Data-, Earth) can be connected in either of two different terminal slots. Connect

each cable to the more convenient set. Never try to connect two cable cores in the same slot: this will cause damage and is likely to result in an unsatisfactory connection,

b.	The clock for the Econet will normally be installed near the middle of the network. (This is particularly important on long networks.) The network is split into two halves at this point, with the clock box linking the two halves together. This is normally achieved in one of two ways:

i	An SJ Research Split Socket Box is installed at this point; see the notes on Split Socket Boxes in this leaflet.
ii 	A socket box is connected to each half of the network at this point, with no direct connection between the two boxes. Standard Econet leads are used to connect each socket box to one side of the clock box.

See, also, the Application Note on Econet Network Topology.

Network Components

Twin Socket Box
This is fitted with two 5 pin DIN sockets. The Twin Socket Box is the most widely used component on the network, since it provides the sockets into which the networked computers and servers are plugged.

Secure Terminator Box
It is necessary to install an Econet Terminator at both ends of the Econet network cable (see Application Notes). This can be plugged into a “standard” Econet socket; functionally there is no reason why you should not have a Twin Socket Box at the end of your network and plug your Terminator in there. However, many Network Managers prefer a secure mounting for the Terminator, this product allows the Terminator to be fitted inside the mounting box. Notice that the circuit board is provided with two pairs of IDC blocks. You are unlikely to have a use for the second pair; however, it is possible to use the box as a Secure Connector Box part-way along the network. A “standard” Econet lead is plugged into the internal socket; the lead is laid into the small hole in the end of the box and the box lid is secured in place. (You might wish to provide such a secure connection where the file server is plugged into the network).

Split Socket Box
This item looks very similar to a Twin Socket Box with two short wires coming from its top. However, unlike the Twin Socket Box, it has no electrical connection between its two sockets / two pairs of IDCs. Each pair of IDCs provides connection to one of the sockets on the board; each socket on the board is also connected to one of the leads which emerge from the top of the box.

The most common use of the Split Socket Box is in conjunction with the Econet Clock Box, where this is installed away from the end of the network. The two arms of the Econet are run back to the Split Socket Box, and one arm is connected to either side of the circuit board. At this stage, there is no electrical connection between the two arms of the network. The two short leads emerging from the top of the Split Socket Box are then plugged into the two DIN sockets on the Clock Box (it may be convenient to fix the Clock Box to the mounting surface above the Split Socket Box). The clock box links the data lines on the two arms of the network, and provides a clock signal for each arm.

The second use for Split Socket Boxes is to allow sections of the network to be isolated. This can greatly facilitate fault finding, especially on a large network. The main Econet cable is connected into one side of the socket box, and wiring is continued from the second set of connectors. It Is essential that the cable is cut at the Split Socket Box. In normal use, the short lead from one side of the box is plugged into the socket on the opposite side of the box, thus linking the two sections of the Econet cable. If it becomes necessary to isolate the network beyond this point, the short lead is removed and replaced by a Terminator. Note that it is only the network on the side of the Split Socket Box closer to the Clock Box which will remain useable, and it is the socket on this half of the socket box which must have the Terminator installed. Clearly, when a Split Socket Box is used in this way, only one of its short leads will be required and users may prefer to disconnect the second lead from the circuit board. This should be done by carefully unsoldering the lead.

We strongly advise that a Split Socket Box is installed wherever the main Econet cable passes out of a building, to facilitate the isolation of the “remote’ section of the network.

Transient Suppressor Box

The Econet interface components in all equipment connected to the Econet network are susceptible to damage from high voltages induced on the Network cable. Transient Suppressor Boxes (TSB’s) contain fast-acting diodes which conduct when a high reverse voltage is applied. During a lightning storm, ‘transients’ (short-duration burst of high energy) can be generated in the main Econet cable. These will travel along the cable, and can contain enough energy to destroy the network driver circuitry in the computers attached to the network. When the transient passes a TSB the diodes direct the energy to the earth terminal in the box and so to the building’s earth system. This reduces the energy of the pulse travelling along the network cable to the extent that the network hardware should not be damaged. In this way, the TSB acts as a barrier to high-energy spikes.

It should be clear that the effectiveness of the TSB depends on a very low-resistance path for the electrical energy to sake to earth. It is essential that the Earth terminal on the TSB’s printed circuit board Is connected to a suitable mains earth. The best place to connect the earth terminal to is the main earthing terminal on the buildings electrical supply as this will be the reference used by all computers when they are plugged into the mains. It is possible to use the earth connection on a nearby power socket, but this is not recommended since it allows fault currents from that area of the mains installation back onto the network wiring. Earthing stakes driven into the ground are also unsatisfactory. Even if a good earth contact is maintained, severe problems will arise if the building’s main earthing system is not perfect; in particular if there is a voltage difference between the mains “earth” connections at different points on the network. (This situation can arise, especially when equipment at different points on the Network is fed from different mains supplies; e.g. when a network serves more than one building. Such problems should be referred to an electrical contractor.)

To allow rapid dissipation of transients, an adequately heavy cable should be used to

connect the TSB’s earth terminal to the earthing point. We recommended 7/0.67mm (2.5mm2) cable. Also, as the distance from the TSB box to the earth point increases it becomes more important to use a heavier cable.

Remember that, to protect a network correctly, the TSB must be between the computers and the source of transients; placing a TSB so that there are computers on either side of it will not protect both sides. TSB’s are particularity necessary where cables pass outside a building (even more so if they then run above ground). In this situation, a TSB should always be fitted immediately before the cable leaves one building and immediately after it enters the next building. It is also strongly recommended that a Split Socket Box is fitted immediately before the transient suppressor box wherever the network leaves a building (in this sense, the network “leaves” the building which is closer to the Econet clock and “enters” the building further from the clock). See Fig. 9. In this way, should a fault develop in the further section of the network it can easily be isolated, leaving the section of the network closer to the clock functioning.

If large transients cause one or more of the Transient Suppressor diodes to fail, they will do so by going “short-circuit”. While this will normally prevent the network from functioning, it will also continue to protect equipment connected to the network against damage from further transients. Nevertheless, it is important to realise that the TSB’s cannot protect against long-duration high voltages (e.g. an accidental short circuit between the Econet cabling and a source of mains voltage) as the TSB diodes will not withstand sustained high—energy faults.

A Technical Report, Line Drivers, Earth Potentials and Transient Suppressors contains additional and more detailed information on the causes of failures in the Econet interface components. Copies of this report may be obtained from the Technical Support Desk at SJ Research.

Important Notice:

The use of semiconductor transient suppressors is accepted technology for the protection of electronic equipment against externally induced transients, and SJ Research uses its best endeavours to specify and supply the most suitable devices for this purpose. However, SJ Research can accept no responsibility for any damage,

however caused, to any equipment connected In any way whatsoever to an SJ Research Transient Suppressor.

Econet Network Cable

The cable used for Econet should be “twin twisted pair” (i.e. with four cores, two twisted into one pair and the other two twisted into the second pair), or “twisted quad”. On “twisted pair” cables it is essential that one twisted pair is used for the Econet Clock signal while the other pair is used for Econet Data. On “twisted quad” cables, the diagonally opposite conductors must be paired (i.e. the two cores carrying the clock signal are diagonally opposite each other, as are the two cores carrying the data signal). These cores must have an overall screen: in some cases this is a wrapping of aluminium foil, while in others it is a braid. There is no functional advantage in a braided screen either in performance or in the cable’s level of RFI emissions. On the other hand, a cable with aluminium foil screening is very much easier to install, since it is much easier to remove the insulation at the points where the Econet boxes (of whatever type) are to be fitted. A drain wire will normally run in contact with the insulation, to provide a convenient means of electrical connection. This wire will also serve as the ground connection for the Econet signals.

It is also better if the individual cores are stranded, rather than single core, since this gives a more flexible cable whose cores are more resistant to fracture. An defective core cross—sectional area of 0.6mm2 is recommended, so that the total resistance of the main network cable is not more than a few tens of ohms. The cable must have a characteristic

impedance of 100. The following table shows the most common Econet cables. If you are adding to an existing network you should check your current cable carefully to determine its colour coding; make sure you identify which pairs of cores are twisted together. Clearly, any network fault-finding will be simplified if you use the same type of cable throughout your installation.
	
Signal	BICC / RS
Cable *	SJ Research
Cable		
Data +	White	Green	*Twisted pair	
Data -	Orange	Red		
Ground	Drain	Drain		
Clock +	White	Yellow	*Twisted pair	
Clock -	Blue	Blue		
Screen	Braided	Foil		
*BICC and RS cables. The white cores of these cables may
be “traced” in the colour of the core they are twisted with.

Figure 10.  Econet Cables: Specifications and Colour Codes

The SJ Research Econet Cable is manufactured specially for this purpose, with foil screen and stranded cores; it has a resistance of only 3 1ohms/km and is suitable networks of any length, up to the maximum for Econet of 1km total length (longer networks are possible but not recommended).

A B.I.C.C. cable was originally supplied by Acorn Computers Ltd. for Econet use. This was a heavy cable (also suitable for very long networks) but with braided screen and solid core, making installation relatively difficult. We understand that B.I.C.C. no longer stock a suitable cable.

The R.S. Components cable (Type 367-921) is similar to the B.I.C.C. one, above, but smaller and higher resistance. Only suitable for networks up to about 300m total length.

Note, also, that cables thinner than those specified may not make reliable contact with the holes of the IDC blocks.

Application Notes
Econet Network Topology

Econet is a bus network, which means that sockets are connected along a single cable. In other words, the Econet network must be linear, with no spurs. It is NOT legitimate to ‘Tee-off’ for each bench; the cable must be run to the furthest extremity of any peninsula and then back again. Similarly, the leads used to connect computers to the Econet sockets should be short - certainly no more than 2m.

Every Econet network must be fitted with a clock, and must have terminator units at the two

ends of the cable. The Econet clock unit has two outputs. It is possible to plug a terminator into one of the clock outputs, and to plug the other clock output into one end of the network, the second terminator must be plugged into the further end of the network. More usually, terminators are fined at both ends of the network, and the clock is installed towards the middle of the net; this option is the one described in the above instructions. These two alternatives are shown in Fig. 11.

The rate at which data is transferred across the Econet depends on the speed at which the clock is running. On a short network the maximum clock speed is determined by the type(s) of computer connected to the Econet; in this case the position of the clock will have no effect on network performance. On a longer network, the maximum clock speed will depend on the distance from the clock to the further end of the network. Clearly, in this case the highest speed can be achieved with the clock at the mid-point of the network cable. Full information on setting and optimising dock speeds is included in the instructions for SJ Research Clock Boxes, and for SJ Research Econet Bridges; some information can also be obtained on request from the Customer Support Desk at SJ Research.

When extending an Econet network, you must preserve the linear topology. You may extend from the end of the network, or by inserting a new loop of cable part-way along the network (one convenient way of achieving this is by placing two socket boxes side by side the existing cable runs into the first one, the new loop runs from the first one into the second, and the existing cable then runs on from the second box). When extending an Econet, you may need to re-position the clock to optimise its clock speed. Longer Econet networks, and non-linear topologies, can be obtained by using Econet Bridges. Such possibilities are described in the instruction manual for the SJ Research Econet Bridge.

Tools for Econet Installation

Stripping the Cable: At each socket box it is necessary to strip off a length of the outer insulation of the Econet cable. We recommend the stripping tool available from RS Components, part number 547-442, for this. In using this tool, it is important to adjust the depth of cut carefully, since too deep a cut will damage to the drain wire which provides the Econet earth connection. In addition, if cable has been installed by drawing through conduit (or similar) then the installation process is likely to have stretched the outer insulation of the cable, reducing its thickness. In this situation you are advised to reduce the depth of cut of the stripping tool from the setting required for cable “on the drum”. In the absence of this tool, the cable can be stripped by careful use of a Stanley knife (or similar), or even with a safety-edged razor blade.

Installing Sockets: The plastic insertion tool supplied with the socket boxes is quite suitable for this, and with a little care one tool will survive installing several socket boxes. However, a professional installation tool is available from SJ Research and we recommend this for ease of installation on larger networks. This tool is fitted with a cutter which normally cuts the core of the cable where it emerges front the IDC block, and a plastic clip to prevent this cutting action. Since you do not wish to cut the emerging cable on an Econet installation, we strongly advise securing this clip firmly In place with insulating tape.

Laying-in Econet Cable

When feeding Econet cable through conduit, a small quantity of a suitable lubricant (e.g. RS part number 544-077) can easily ease the process. NEVER use washing up liquid or other liquid soaps for this purpose as these can lead to the cable insulation breaking down prematurely.

Figure 12. Mounting Econet Boxes on a Fascia Board

The most difficult part of installing Econet is avoiding cutting the cable at each socket box. Probably the neatest solution to this is to mount the sockets on a fascia board, which is secured to horizontal battens which are, in turn, screwed to the wall. Melamine (or similar) faced chipboard, as sold for DIY shelving, is very suitable for this. It is fairly easy to out cable slots in this. However, since you can thread the cable before securing the board to the mounting batten, it is not too difficult to thread the cable in and out at each socket. This option is illustrated in Fig. 12 (right).

Other approaches involve the use of plastic box trunking, and adapting the cable entry slot

in each socket box. The first technique is to run lengths of trunking between the socket boxes; this is illustrated in Fig. 13. which also shows how the cable cut-out in the socket box needs to be altered.

However, a better solution is often to run the trunking below the boxes, as shown in Fig. 14. This has the advantage that additional cables (not passing through the Econet boxes) can be run in the trunking. Clearly, a section of the side wall of the trunking needs to be cut out at the position of each socket box. Against this. trunking does not need to be cut to length for each box and in practice this approach can offer considerable time savings.

It is possible to use a file to alter the cable slots in the Econet boxes, particularly for the alteration shown in Fig. 13. However, the most usual approach is to use a small hacksaw to cut down as far as required from the existing slot (in either approach). A Stanley (or similar) knife is then used to score deeply along the bottom of the section to be removed. The unwanted plastic is then carefully snapped off with a pair of pliers. Similarly, when removing part of the side wall of the trunking the easiest approach is to cut down the side wall with a hacksaw at either end of the section to be removed. Score fairly deeply along the corner of the trunking between the two cuts, and break off the unwanted plastic. This approach is only advisable if the trunking is no deeper than the Econet boxes (20mm), and this should be considered when selecting suitable trunking.