Fig. 1 shows an example of the automatic block system for a double-track section. Here, the tracks inside and between stations are divided into a number of block sections in accordance with the train operation plan, and home, departure or block signals which are automatically controlled by track circuits are installed at the leading edge of these sections
This block system integrates blocking with signalling, and signal usage is as follows.
* Home signals: These display signals for trains entering stations
* Departure signals: These display signals for trains departing from stations
* Block signals: These display signals for trains entering block sections
* Train stop markers: These indicate the stopping limit when departure signals are not erected at the prescribed position.
Stations without turnouts are intermediate stations where operation handling is not performed, and home and departure signals are not normally installed in these stations.
Fig. 1 Automatic block system for double-track sections
(2) Block systems for single-track sections
Single-track sections differ from double-track sections in that trains are operated in both the in-bound and out-bound directions over a single main track. Therefore, these systems require block functions not only for continuing trains but also for opposing trains.
The main types of block systems used for single-track sections are described below.
a Automatic block system (type A)
This system is used for trunk lines. Like automatic block systems for double-track sections, track circuits are installed continuously in and between stations to automatically control home, departure and block signals.
The traffic direction is set by switching a traffic lever located at an adjacent station. Block functions for opposing trains consist of setting the traffic direction so that stop signals are displayed on the opposing block signals and departure signals of the adjacent station, and locking the traffic direction so that it cannot be changed when trains or other vehicles are between stations.
