TELEPHONE KIOSK
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It appears that BT decided to rewire some of the telephone kiosk estate at some point in the past. When rewired, the wiring system was changed from a Class 1 system, which used an earth wire to a Class 2 system which uses un-earthed equipment, which is double insulated. The red plastic mains intake cover may also replaced with a full width metal box, which also covered the incoming line cables. The mains intake is fitted with a low current fuse and they fitted a Double Pole isolator switch (which was fused at a low rating) which was wired to a terminal block. All the fittings installed have no exposed metal work including the external screw-heads. The light fitting was changed to a Double Insulated type and this was wired to the terminal block, along with the Coin Box power supply. Both equipments could be isolated by the use of the Double Pole switch. This is all working at 250 volts AC. There is nothing wrong with the above setup but users must be mindful that only Double Insulated equipment can be used and that this will be marked “Class II”, “double Insulated” or the showing symbol of the concentric square. Any three pin plug used on double insulated equipment will have a plastic earth pin. Another point is that the electrics are also fused with low current fuses and the wiring is designed for this rating. If you are to utilise existing kiosk wiring it is better to get it checked by a qualified electrician.
Typical electrical layout in a Class 2 installation
Close-up of the Terminal Plug housing (left) and the
Double Pole Isolator switch (right)
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Last revised: September 13, 2024FM |