CABINETS, CROSS CONNECTION No's 1, 2 and 3 | |||||||
IPOEE
Article on Subs Cable Distribution - 1939 IPOEE Article on Subs Cable Distribution - 1944 Initially wiring was all overhead, but as more people went on the phone the number of aerial cables became obtrusive and heavily congested.
Before the second world war flexibility in the cable network was afforded by the use of "multiple teeing" and "auxiliary joints" and in towns cable distribution heads were used. These distribution heads consisted of water tight iron casings, which could be opened, but re-routing a cable was still difficult and working on the case could cause faults on other lines. Distribution heads are pictured to the right. Multiple teeing is a system where a proportion of the cables pairs from the exchange Main Distribution Frame (MDF) are teed together at joints and so are connected to more than one Distribution Point (DP). This system is termed "non-tapered cable", that is, the main cable does not reduce in size at every spur junction point. The object of the auxiliary joint method is that having connected the permanent pairs from the MDF to DP through a permanent joint, a proportion of the pairs are connected via an auxiliary joint where any alterations in requirements can be made subsequently. Changes in the growth pattern meant that most changes were made in the permanent joint or between the MDF and the DP and not in the auxiliary joint as expected. In certain instances floor standing cast iron cabinets were used and these were square in shape and called Service Cabinets. These are shown in the pictures below.
With the use of the telephone rapidly expanding, from 1945 onwards a new method of distribution was adopted that was flexible and able to cope with growth. Cabinets were introduced and were generally the first cross connection point from the exchange. They could be used to feed Pillars which in turn would have fed the Distribution Points (DP), but could also feed Distribution Points directly. A DP was the final connection to the underground cable and can be found at pole tops, on walls and in customers premises. The Cabinets were called the "Cabinet, Cross Connection"
and consisted of the following range:- The cabinets were and still are painted dark green. The Cabinets and Pillars afforded flexibility in the network as any incoming wire could be connected to any outgoing wire. The connection made by a piece of twisted two wire called a "jumper wire". Before the 1970's Cabinet terminations were actually screws which clamped the jumper wire or in the case of a through connection (i.e. wire 10 to wire 10) two metal bridging pins were used (See picture further down page). If the screws were over tightened the heads would shear off, to prevent damage. To prevent over tightening of the screws a torque screwdriver (Torquemaster Screwdriver 22oz) was provided for those working in Cabinets and Pillars.
Bridging Pins No. 1 - Used on open type assembly - obsolete. When jumpering between connections, 12.5lb two wire was used. This was originally called Wire, Equipment 2711 which was coloured Red and Blue. Wire Jumper 6541, coloured Yellow and Blue was used later on. As telephone penetration rose, Pillars were phased out and the Cabinets fed the Distribution Points directly. Cabinets were painted dark green and made of cast iron. Today they are made of steel. Cables from the exchange are terminated on the 'E Side' of the terminating strip whilst the outgoing distribution cables were terminated on the 'D Side' of the strip. The largest Cabinet (No. 3) can take 800 pairs in and out and the largest Pillar, 200 pairs. Click here for more information on Cabinets. In the early 1970's the screw style terminal blocks were replaced with plastic formers and the cable wires just pushed through numbered holes and left hanging. Connection between wires was made compressed crimps, called Connectors, Wire Insulated No. 1 (white coloured) or Connectors, Wire Insulated No. 1A (blue coloured and grease filled (See picture below). These connectors were crimped with a tool called a Crimpers, Connector, Wire, Insulated No. 1 or a Pliers, Crimping No. 2, which can be checked by a Gauges, Check 2.1mm. Click here for more information on Crimps Two styles of plastic formers were field trailed and were known as the Midland and Yorkshire types. The Yorkshire type was adopted as the standard.
Cabinet, Cross Connection No. 2
Old style open type connection strips
Pillar with crimped connections (Yorkshire Area).
Strips Connection No. 1 showing layout and numbering.
Yorkshire style mounting showing wire routing
Yorkshire style mountings - close up
Pillar (100 pairs) showing screwed connections
Cabinet, Cross Connection No. 1 Close up of screw type blocks in a Cabinet, Cross
Connection No. 2 with
enclosed strips.
Cabinet, Cross Connection No. 2 Cabinet, Cross Connection No.3 with local footway joint box open to show cable
joints.
Midland Region layout in a Cabinet, Cross
Connection No. 1 (single door).
Crimpers, Connector, Wire, Insulated No. 1 - tool used
with Connectors, Wire, Insulated No. 1
Later Cabinet, Cross Connection No. 1
Cabinet, Cross Connection No. 3
Cabinet, Cross Connection No. 3
Box Building team installing a new Cabinet No. 3 in place of a Cabinet No. 1
New cabinet ready to be lifted into position.
New cabinet being lifted into position.
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Last revised: April 21, 2023FM2 |