Page 409 - IRSEM_Main Book

(l) If section is installed with Embedded type Block working i.e. Block working
built into Electronic Interlocking, VDU kept in ASM room shall have Block

Indication display in both the VDU with hot standby feature. Display
Descriptions shall be followed as per Drawing No. RDSO/S/32019.

18.1.2 Special Requirements of Single Line Token Block Instruments

(a) Fixed Indications: The instruments shall be provided with visual indication
clearly giving the following indications:

(i) When the instruments are normal and there is no train in the block
section, "Line Closed" at both the stations.

(ii) When Line Clear for a train to leave the Block station in rear has been
given, "Train Coming From" at the receiving station.

(iii) When Line Clear for a train to leave a Block station has been received
from the Block station ahead, "Train Going To" at the sending station.

(b) Current Indicator: An indicator, indicating the polarity of current, shall be
provided to indicate incoming and outgoing line currents.

(c) Operation: "Train Going To" and "Train Coming From" - The instruments shall
be such that the co-operation of the Station Master at the other end of the
section shall be necessary. Even with the co-operation of the Station Master
at the other end, the Station Master has to go through one or more definite
moving operations on the instrument in addition to working of bell plunger.

(i) Before he can grant Line Clear to the Station Master at the other end of
the section to release a token, or

(ii) Before he can obtain Line Clear and extract a token.

(d) "Line Closed": Both the instruments shall be restored to normal before a
further operation of setting the instrument to "Train Going To"/"Train Coming
From" can be carried out. It shall not be possible for the instruments at
either end of the section to be restored to normal without the co-operative
features indicated in para 18.1.2(c).

(e) Operation of "Line Clear" Receiving and Granting Mechanism: It shall
not be possible for the mechanism which permits a "Line Clear" to be
received and that which permits a "Line Clear" to be granted to be in
operation at the same time.

(f) The instrument that is set to "Train Going To" for initiating a train movement
shall be the first one to be restored to "Line Closed" on complete arrival of
the train at the receiving station.

(g) Extraction of Token: It shall be possible to extract one token only when
the instrument has been set to "Train Going To". It shall not be possible to
change the "Train Going To" condition until the token has been inserted in
one of the instruments of the Block section.

Chapter 18: Block Instruments, BPAC & IBS Working Page 357 of 535