Page 432 - IRSEM_Main Book

DN-MAIN DN-REDUNDANT
FROM TO TRACK SECTION FROM TO TRACK SECTION
DNDP1-A DNDP3-A DN-AC-A DNDP1-B DNDP3-B DN-AC-B
DNDP2-A DNDP3-A 7 AC-A DNDP2-B DNDP3-B 7 AC-B
DNDP2-A DNDP4-A DN-BPAC-A DNDP2-B DNDP4-B DN-BPAC-B
DNDP1-A DNDP4-A DN-SPT-A DNDP1-B DNDP4-B DN-SPT-B
Fig 2. Boundaries of Track Section

Dual detection has been provided with redundancy for all other equipment as well as
communication media. The Typical IB section consists of Three track sections in each
direction.

(i) AS track section, which starts from the foot of LSS and ends at 400 meters ahead of IB
home signal (DN-AC)

(ii) IB track section, from the foot of the IB home signal to 400 meters ahead of the signal (7
AC)

(iii) BPAC section, from foot of the IB home signal to 180 meters ahead of the home signal of
the ahead station for proving block overlap (DN-BPAC). A supervisory track section (DN-
SPT) covers all these three track sections, which is used for second level of reset as
explained in later sections.

Chapter 18: Block Instruments, BPAC& IBS Working Page 380 of 535