Hoping to be of further help, Dot93, whilst not moving to things of which you may already be aware; - carrying the foregoing points about Absolute Block etc. into Track Circuit Block matters,
on the vast majority of TCB running lines the signal section from one main stop signal to the next is the equivalent of the archetypal 'most advanced starting signal of one box to the outermost home signal of the next box in advance', box-to-box AB section.
Whilst out of any group of these signal sections, mostly, they will be under the control or supervision of one single signaller, there are, in areas signalled from multi-staffed, moderate-large signal control centres*, inevitably some sections which effectively form the hand-over point between individual signallers' areas of either the same, or different, SCCs.
* - (the term 'signal control centres' can apply equally to control locations variously known as 'power box', 'power signal box', 'signalling centre', 'area signalling centre', 'rail operations centre', and possibly others.)
Traditionally (say approx. 1930s - 80s) most TCB series of automatic and semi-automatic signals between areas of directly controlled signals, and therefore also their Signal Post Telephones, were considered and arranged to be the responsibility of the 'advance' signalman whose next directly manually controlled area ahead they were on the approach to, and this meant that the Up and Down signals in such 'hand-over' areas were supervised by different signalmen. But with the advent of electronic / computer-based, rather than relay, interlockings, and engineering considerations bringing about a preference for interlocking (and so, usually, signallers) boundaries to be at roughly the same place on all tracks, the 'approach to' practice mostly no longer holds good for new works from approx. the 1990s onwards.
Now, concerning the question of 'rear or advance signaller' protection and contact in case of mishap, TCB systems should automatically protect in rear of a train in all but the most exceptional circumstances.
As regards drivers' communications in the event of problem, SPTs, and where provided other lineside 'phones, normally connect directly to the relevant signaller.
But AIUI all traction types on the network are now required to be equipped with working radio system(s) of one or other kind (can be more than one : - but I believe well on the way to universal provision and use of the GSM-R system), which include affording discrete direct communication to the signaller and are usually arranged to automatically ensure driver-initiated contact goes to a correct signaller for the location, including priority emergency call ability; also of these, the GSM-R system in case of emergency can simultaneously alert more than one signaller who may, depending on circumstances, be in a position to initiate appropriate safety action.
Hope all this waffle is of help / interest, while doubtless there may be clarifications / comments which others can add.
Last edited by StevieG
on Wed Nov 23, 2016 12:57 am, edited 1 time in total.
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