BS 6556-2:1985

Foreword
Committees responsible
Specification
1 Scope
2 Definitions
3 General conventions
4 Data link configurations
5 Channel allocation
6 Data rate
7 Modulation parameters
8 Line spectrum
9 Modulator
10 Demodulator
11 System performance
12 Cable connections
13 Environment
14 Line circuit parameters
15 Marking
Appendix
A Cable parameters used for system performance test
Tables
1 Manner of modulator operation
2 Manner of demodulator operation
3 Performance tests
Figures
1 Simplex operation
2 Duplex point-to-point operation
3 Multi-drop operation
4 Resistive node
5 Frequency shift keying (FSK)
6 Originate channel spectrum limits
7 Answer channel spectrum limits
8 Modulator configuration
9 Demodulator configuration
10 Performance test configuration
11 Generator of 511 bit pseudo-random data
12 Core configuration of cable

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

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.