Page 411 - IRSEM_Main Book

(c) 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. The instrument shall be such that a button in
addition to the bell button shall be operated by the receiving station for
setting both the instruments to the "Line Closed" condition. This feature can
be dispensed with where an automatic device of closing the Block section
is provided.

(d) 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.

(e) Tokenless block instruments shall be provided with

(i) Audible indicators to warn the receiving station.

 When the train enters the block section at the sending station.

 When the train has passed the Home Signal at the receiving station.

(ii) Shunting key suitably interlocked with the Block instrument for use as
an authority for shunting behind the Last Stop Signal and up to the
opposing First Stop Signal.

18.1.5 Special Requirements of Double Line Block Instruments

(a) Indicators for Up and Down Lines: The Instruments shall be provided
with Visual indicators separately for Up and Down Lines to show the
following three conditions:
(i) Line Closed

(ii) Line Clear

(iii) Train On Line

(b) Current Indicator: The indicators provided as per para18.1.5(a) may also
serve as the current indicators.

(c) Operation before Granting or Receiving Line Clear: The instrument shall
be such that the Station Master has to go through one or more definite
moving operations on the instrument besides working the bell or plunger
before he can grant Line Clear.

(d) Audible Indicator: Where required, the instruments may be provided with
audible indicators

(i) to warn the receiving station when the train has passed the Home
Signal, and

(ii) to warn the sending station when the train has passed the Last Stop
Signal.

Chapter 18: Block Instruments, BPAC & IBS Working Page 359 of 535