BS 6556-2:1985

This standard BS 6556-2:1985 Low speed digital signals for use in coal mines is classified in these ICS categories:

• 29.260.20 Electrical apparatus for explosive atmospheres

This Part of BS 6556 specifies the electrical input and output characteristics for the transformer coupling of intrinsically safe transmitting and receiving circuits for use in coal mines. These form a low speed digital data transmission link in which data is transmitted using frequency shift keying techniques.

A data transmission system comprises a master and up to 15 physical slaves. The circuits of all stations are galvanically isolated from the line circuits by transformers.

NOTE 1 Each physical slave may support more than one addressable logical slave as specified in Part 3 of this standard up to a maximum of 15 addressable slaves for the complete system.

This Part of BS 6556 only applies to apparatus where the circuits connected to the transmission lines are designed to be intrinsically safe in accordance with BS 1259, BS 5501-7 or BS 5501-9 as appropriate.

NOTE 2 Where apparatus, which is intended to be used in potentially explosive atmospheres, contains other circuits which are not intrinsically safe, those circuits will have to be given an alternative form of protection in accordance with BS 229, BS 4683 or BS 5501 as appropriate.

NOTE 3 The titles of the publications referred to in this standard are listed on the inside back cover.

Defines electrical input and output characteristics of intrinsically safe transmitting and receiving circuits forming a low speed digital data transmission link in which data is transmitted using frequency shift keying techniques