Restoration - page 6 Princes Risborough North Signal Box
2021 - 2022 Even though early Spring saw the final throes of lock-down restrictions easing following the Covid- 19 pandemic, our team still tried to work outside in the fresh air as much as possible. We started building the wooden platform and upper works on the bracket signal behind the signal box although it will be a while yet before we can attach the actual red signal arms. In late spring we set about the internal electrical wiring needed for the block shelf instruments and lever plungers. The plungers are required so the signaller can release the electrical locks which act in addition to the mechanical locking. Even a 1905 built signal box needs to adhere to 21st century safety requirements! We created the new illuminated diagram of our track layout in the Princes Risborough area and fitted the indicator lights. The siding from points 113 will be put in place during 2023. The next thing to do was run cabling between the electrical relays housed inside the signal box, outside to lineside cabinets which in turn have wires connecting to the actual rails of the track. These 'track circuits' detect the presence (or more accurately, the absence*) of a train and activate (again more accurately, de- activate*) the relays which control the lever locks. *The safety systems employed by all railways are designed to 'fail safe'. That means if something goes wrong with any piece of equipment, it will never allow an unsafe indication or action. A simple example is if a signal wire breaks - the arm will revert to danger, by a combination of weights and gravity. A purpose built testing panel was constructed inside the box from an old office telephone exchange switch panel to simulate the external connections and track circuits thus allowing us to be confident of the wiring integrity prior to the final more stringent testing at time of commissioning. With an eye to the future, we experimented with setting up a 'Block Bell over Internet' (BBoI) system whereby our signaller at Risborough can communicate with the signal box in the box at Chinnor, and vice-versa. Although we do not use this as a 'safety critical' method of notifying train movements, it does add to the authentic sights and sounds inside the signal box as well as providing training for our signallers, ready for when we can connect the two signal boxes via trackside wires. We made more additions and enhancements to the mechanisms on the locking frame which is housed directly under the upstairs operating floor. Throughout the year we continued with seemingly endless task of repainting the window sashes, replacing more newly discovered timber rot. We identified the few remaining areas of brickwork that urgently needed re-pointing and used the correct lime mortar mix to deal with those. All in all it was another year of preparing the station end of the box for its imminent role as the working Princes Risborough Middle Box.
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