Tokenless Block System Basic layout and operation This document is not endorsed by Network Rail. It is NOT for installation, commissioning, testing or maintenance purposes, it is for information only. Network Rail s own documents must be followed at all times, however; this contains re-written extracts from railway standards. Any pictures are copyright of the author. Copyright F. M. Spowart 5/1/2015
Tokenless Block System Page Two of Six Basic Layout of Signallers Block Instrument: The Instrument layout may consist of one of the following types; BLOCK TRAIN IN SECTION TRAIN ACCEPTED A B C A: B: TRAIN IN SECTION C: TRAIN ACCEPTED ACCEPT ACCEPT Commutator switch OFFER ARRIVED OFFER ARRIVED Basic Track Layout: (Your own area will differ on site) UP / DOWN 1 TREADLE 3 5 SIGNAL BOX Z 2 4 TREADLE SIGNAL BOX Y 6 The Relays, Function and Brief Description: Signalbox End Relay Function Normal position Sending (**)NCR Section Clear Relay UP De-energises when a train enters section in specified direction (**), which signifies section is not clear and cannot accept a train. Energises when train has passed. Receiving (**)NCR Section Clear Relay UP De-energises when a train enters section in opposite direction (**), which signifies section is not clear and cannot accept a train. Energises when train has passed. Sending (**)NTxR Block Normal Transmit UP De-energises when train enters section in opposite direction to that specified. Stops transmission of BRxR, and NRxR thus indicating a train to the receiving end. Energising when train has passed clear of the section in opposite direction to that specified at the receiving end. Causes transmission of the (**)NRxR to the receiving end and maintains transmission of (**)NRxR from receiving end.
Tokenless Block System Page Three of Six The Relays, Function and Brief Description (continued): Signalbox End Relay Function Normal position Receiving (**)NTxR Block Normal Transmit UP De-energises when train enters section in opposite direction to that specified at sending end. Energises when train has passed clear of the section in the direction specified and when TRAIN ARRIVED button operated which causes transmission of the (**)NRxR to the sending end. Normalisation process started. Sending (**)NRxR Block Normal Receive UP Energises when block normal in specified direction from receiving end. Receiving (**)NRxR Block Normal Receive UP Energises when block normal to allow move in specified direction. Sending (**)OTxR Offer Transmit Relay DOWN Energises when OFFER button pressed (with commutator button ) for a train in specified direction. Maintained once offer has been made and acceptance received by (**)BCR. Receiving (SECT)BRxR Block Receive Relay DOWN Energises when offer is transmitted from sending end (by NRxR energised). Receiving (**)ORxR Offer Receive Relay DOWN Energises when offer receive for a train in the specified direction from the sending end. Starts acceptance procedure. Receiving (**)ATxR Accept Transmit Relay DOWN Energises when offer received for a train in specified direction from sending end with commutator in ACCEPT position and providing opposite direction starting signal is on, home and distant also on and alight. Transmits an acceptance to sending end. Receiving (SECT)BRxR Block Receive Relay DOWN Energises when acceptance received from sending end. Sending (**)BCR Acceptance Received DOWN Energises when acceptance received for a train in specified direction from receiving end. Maintains transmission of the initial offer allowing the signaler to release the OFFER button. Allows starting signal to clear (the must be proved on beforehand. If the signal is a semaphore, it ensures it has been replaced to normal after the last move in same direction. Receiving (**)QSR Treadle Relay DOWN Operates when a train leaves the section. (**): direction [up or down] as specified on site. Transmission: The actual transmission type is dependent on the area it is installed. It may be by conventional signalling cable, but due to the distance and having no working signalling such as signals and track circuits, it is more likely to be transmitted using a small reed transmission system and then sent down a British Telecom (BT) maintained telephone cable. If the system fails and shows a train in section when it is clear, first of all check that the BT system is showing system healthy. If not, the block will never reset. If the system requires resetting by simulating a train, the block section must be checked to be clear by telephoning* both section signallers to confirm this. But remember, the system could have been tripped by a trolley or road railer etc during a T3 possession, so the PICOP must be asked to confirm the section is clear before resetting. If in any doubt, don t reset the block. A train will be sent through at caution by modified working to check it is clear. The train will reset the block as long as the signalling is set correctly at the end.
Tokenless Block System Page Four of Six It can be reset by simulating a train at any end. The exit route has to be set by the signaller along with the commutator switched to accept. *Even if the tokenless block equipment is situated under or next to one of the section signalboxes, it is best practice to telephone the signaller to ask if the section is clear, this will then be recorded should any incidents arise. Always make an entry in the loc/rr/train register to state it has been reset and why. Flowchart Operation: From the diagram on page two consider signalbox Y to be the sending end, and signalbox Z to be the receiving end for the purpose of following this flowchart. Signaller at Z who is expecting the next train places commutator to ACCEPT. (Note; both commutators may normally stand at accept). BOXES ON LEFT SIDE SIGNIFY SENDING END BOXES ON RIGHT SIDE SIGNIFY RECEIVING END (UP) NCR UP (DOWN) NTxR UP (DOWN) NRxR TRANSMIT Note: the term transmit is when a reed transmission system is used Block indicating (DOWN) NCR UP (UP) NTxR UP (UP) NRxR TRANSMIT Signaller at Y places commutator to, and presses and holds OFFER button. (UP) OTxR UP (DOWN)NRxR DOWN. Stops NRxR transmitting Transmits offer to (YtoZ) BRxR (UP)ORxR UP Opposite starting signal, home and distant signals proved on and alight (UP)ATxR transmit (UP)BCR UP (ZtoY) BRxR transmit
Tokenless Block System Page Five of Six Offer button released Block indicating TRAIN ACCEPTED Starting signal can be released Train enters section Track circuits occupy at beginning of the route (DOWN)NTxR DOWN Ceases transmission of (YtoZ)BRxR (DOWN)NCR DOWN Ceases transmission of (DOWN)NRxR (UP)NTxR DOWN Block indicating TRAIN IN SECTION Block indicating TRAIN IN SECTION No transmissions are being made with train in section (fail-safe method) If the sending signaller was to try and offer another train, the offer transmit (UP)OTxR will operate, but this will be prevented from being transmitted by the (DOWN)NTxR being de-energised (this relay will not energise until the out-of-section procedure is followed). If the receiving signaller was to offer a train with one already in section, this will operate the (UP)OTxR, but again this will be prevented from being transmitted by the (UP)NTxR being de-energised, again this will not energise until the out-ofsection procedure is followed. Train leaves the section at the receiving end
Tokenless Block System Page Six of Six Train occupies track circuits Signaller at Z turns commutator to Train operates treadle (UP)QSR UP Signaller at Z presses and holdstrain ARRIVED button (UP)NTxR transmits to sending end (UP)NCR UP (DOWN)NTxR UP Transmits BLOCK to receiving end Block indicates (DOWN)NCR UP (& holds (UP)NTxR) (UP)QSR DOWN Signaller at Z releases TRAIN ARRIVED button Block indicates System has now reset and is ready for next movement Tail Lamp operation: Some installations have a tail lamp system included where the end of the single line section is far from the signalbox. The signaller acknowledges the end of the train (with the inclusion of the tail lamp to signify this) via a TV screen (transmitted by CCTV) by pressing the Tail Lamp Acknowledge button, or using the emergency reset procedure if for any reason the tail lamp is missing or the signaller misses it by not watching the TV screen, or loss of picture. The tail lamp acknowledge must be pressed to enable the NTxR to energise to normalise the block. >>>E N D<<<