Railway Staff Protection Keyswitch :- Staff Protection Keyswitch(SPK) units are key operated switches with green LED indication light. It consists of two permanent traffolyte labels showing area that it protects. One will be affixed to the inside of the door and the other attached to the key hob. The Keyswitch has two positions “Normal Working(Area not protected)” and “Area protected”. The Key is captive in the normal working position. The Keyswitch type is of Castell KS-20.
They are normally located at the ends of the platforms. At places where the area of protection is controlled by multiple SPKs, it shall be located as per the site requirement. The SPK unit will be mounted into spare boxes within the headwall unit on the JLE section and within a lockable enclosure (located in Non passenger area of station) on OJL section. The detail of areas requiring protection by Keyswitch shall be agreed with UAM.
The TBTC system monitors the status of all Keyswitches in the normal working position. When any Keyswitch operation is detected, the TBTC system shall close the relevant tracks in such a way that no approaching train shall be given LMA closer than a safety distance to the protected area. Any train within or with a LMA into protected area shall be emergency braked to a stop. Points within protected area shall be prevented from moving automatically or when commanded.
Local commands (LCP Mode) will be permitted to operate the points. TBTC system also commands lighting of indication at the SPK unit(s). The protection shall apply until the key is return to the lock and Keyswitch moved to normal working position.
The system behavior to this device is identical to other emergency stop devices. There is no override for SPKs. The status of the Staff protection keyswitches will be displayed at SMC workstations.
When the staff require access to the area of track protected by SPK, they shall turn the key to the “Area protected” position and remove the key from Keyswitch.
When the SPK operation is detected by the SCS and reported to the VCC, the VCC will close relevant tracks and command the SCS to turn ON a vital indicator at the SPK unit in confirmation.
The staff entering the track under SPK protection shall ensure the vital indication is lit and must take the unique key with them to ensure the protection remains.
The vital indication is illuminated at all SPK sites, if any key is removed that covers the same area of protection.
After return, the unique key will be inserted back in the Keyswitch and turn to normal working position. This operation is vitally detected by SCS and reported to VCC. The tracks can be reopened by VCC/SMC operator.
As per Relay Rack Requirements Specification HwRS.RR. 1231, the IMC outputs from the SCS Electronics Rack shall control all relays detecting ESDs except Staff Protection Keyswitches. Hence the power supply need not be from 110V AC (S/W).
As per Relay Rack Requirements Specification HwRS.RR. 826, the Relay Rack shall continue to monitor the keyswitch status even when the SCS Electronics Rack is powered down.
As per signalling principles 5.1, The keyswitch status shall be retained even if the interlocking or other associated systems are powered down and re-started.The relay rack shall report the status of multiple SPKs in series as a single input to each relevant SCS Electronics Rack, when the SPKs protect the same area, as per the common tables. Such arrangement exists at North Greenwich.
At Charing Cross for staff protection area k2, the circuit consists of three staff protection keyswitch devices. Two keys are to be installed, in normal service position these are located in keyswitches k2a & k2c.
One unique key is capable of operating two separate locks only, one to the south end of platform 3(k2b keyswitch) and one at chx p10 trap points (k2c keyswitch).
They operate in parallel, if the key is in either lock then the track can be opened, if the key is in neither lock then the track shall be closed.
The other key is only capable of operating the lock located to the south end of platform 3 (k2a keyswitch).
This lock will operate in series, with the two other locks in parallel. If at any time this key is in the lock, the track can be opened with a key in either of the aforementioned locks(k2b & k2c), If at any time this key is out of the lock the track shall be closed regardless of the conditions presented by the other associated locks.