The absolute block system does not replace the use of any other form of signalling, such as fixed signals, hand signals, or detonators ( and, in fact, usually relies on fixed signals ).
22.
A special speed limitation of 30 km / h had been enforced by means of an " M40 " mandatory alert, but the fixed signals reported condition normal and the train failed to slow down.
23.
A points indicator may only be passed if it displays the correct route indication for the tram concerned and, where fixed signals are provided, if both points indicators and fixed signals are set for the correct route.
24.
A points indicator may only be passed if it displays the correct route indication for the tram concerned and, where fixed signals are provided, if both points indicators and fixed signals are set for the correct route.
25.
A fixed train stop that is the last one on a running line in the reverse direction may, despite its name, be suppressed, as is the case with the associated " Fixed Signals " on the Sydney network.
26.
Technological advances including mechanical fixed signals in the 1840s, the electric telegraph and block working in the 1850s, and proper mechanical interlocking from 1856, allowed safer, more expeditious train working, and more complicated track layouts to be controlled single-handedly.
27.
The fixed signals consisted of a signal at the station or crossing place, not necessarily placed before the fouling point, which gave permission to enter the station, and an auxiliary signal placed further back which functioned like a distant signal.
28.
In 1874, Spagnoletti's views on contemporary signalling developments were recorded during a discussion of a paper, " On the fixed signals of railways " by R . C . Rapier read before members of the Institution of Civil Engineers on 31 March of that year:
29.
There were no fixed signals, and trains were despatched under the time interval system . [ In the absence of telegraph communication, collisions were intended to be avoided by holding trains back until a specified time interval had elapsed since the departure of the previous train .]
30.
The signalman there had set his signal levers to put his signals to'danger'to protect the shunting at Abbots Ripton, but had not left his levers to set detonators at the home signal, nor did he supplement his fixed signals by displaying a hand-lamp from the signal box.
