Cabinets, Cross Connection No's 1, 2 and 3
|Initially wiring was all overhead, but as more people went
on the phone the number of aerial cables became obtrusive and heavily congested.
Multi-core cables then came on the market and the overhead wires were moved to an underground network of cables. These cables were fed from the exchange and smaller cables were teed into these cables as they radiated away from the exchange. These cables provided no real flexibility as each division was a joint.
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 cast iron cabinets were used and these were square in shape. These are shown in the pictures below.
With 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 generally the first cross connection point from the exchange and they may also feed Pillars which in turn would have fed the Distribution Points. A DP was the final connection to the underground cable and can be found at pole tops and in customers premises.
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 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 was provided.
Bridging Pins No. 1 - Used on open type assembly - obsolete.
When jumpering, 12.5lb two wire was used.
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.
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 was made with grease filled crimps (See picture below).
The largest Cabinet can take 800 pairs in and out and the largest Pillar 200 pairs.
Old style open style connection strips
Pillar with crimped connections (Yorkshire Area)
Strips Connection No. 1 showing layout and numbering.
Yorkshire style mounting showing wire routing
Pillar showing screwed connections
Cabinet, Cross Connection No. 1
Close up of screw type blocks in a Cabinet, Cross
Connection No. 2 with
Cabinet, Cross Connection No. 2
Cabinet, Cross Connection No.3 with local footway joint box open to show cable
joints. The cabinet is immaculate
Midland Region layout in a Cabinet, Cross
Connection No. 1 (single door).
Crimping tool used with grease filled crimps
Box Building team installing a new Cabinet
Last revised: December 20, 2021