Page 421 - IRSEM_Main Book

(l) Block Instrument Telephone: Block instrument telephone, its flexible
cord and the condenser or other means provided for isolating the
telephone from the Block instrument circuit are in good condition. The
isolation is such that there is no direct path for the current to flow from one
circuit to the other.

(m) Receiver diaphragms are not buckled and are at the correct distance from
the pole pieces.

(n) Receiver ear piece fits correctly and is screwed tight.

(o) When a pair of block instruments of a block section falls in different
contiguous Railway/Division, both instruments and their associated
equipment shall be maintained by one agency.

18.8.2 Overhauling of Block Instruments: Periodical overhauling interval shall not
exceed ten years for Single Line Token Block Instruments and seven years for
Double Line Block Instruments and Handle type Single Line Tokenless Block
instruments. Push Button Tokenless Block Instruments, UFSBI Block panel, and
Embedded block working in Electronic Interlocking etc. do not require
overhauling. The associated polarised relay shall also be overhauled along
with the Block instrument.

18.8.3 Block Earths

(a) Block earths and their connections shall be examined at intervals of not
more than one month by the Section Engineer(Signal) and at intervals of
three months by the Senior Section Engineer(Signal).

(b) Block earths shall be tested for resistance at intervals of not more than 12
months by the Section Engineer(Signal) or Senior Section Engineer(Signal) in
accordance with Annexure: 19-A3. Where the resistance exceeds 10
ohms, action shall be taken to reduce the resistance by providing additional
earths in parallel.

(c) In AC electrified areas, two different Earths shall be provided for Discharger
and Block Earth.

(d) The four Terminal Condenser used in filter shall be connected in such a way
that the DC circuit is completed through the plate or foil of the condensers.
It shall be ensured that any break in the foil or Earth connection, which
might affect the efficiency of the filter, puts the circuit itself out of use.

Chapter 18: Block Instruments, BPAC & IBS Working Page 369 of 535