scope:

GENERAL 

This specification applies to transformer-rectifier units, suitable for general railway signalling purposes, whose nominal mean output voltage does not exceed 175 V irrespective of input voltage and output current rating.

The unit shall consist of a transformer, a full-wave bridge-connected rectifier and fuses; all suitably connected and mounted and with the appropriate terminals for external wiring and earthing purposes.

The requirements of this specification are varied by Appendices for transformer-rectifier sets for special purposes:-

Appendix 4 : electric point machine operation.

Appendix 5 : non a.c. immune track circuit feed set.

This specification does not cover all the transformer-rectifiers included in BRB catalogue classification no. 86, section 51.

In particular it does not cover transformer-rectifiers for:-

(a) output voltages less than 10 V nominal

(b) telecommunications purposes

(c) signal lighting

(d) intermittent duty cycles

(e) regulated and/or smoothed d.c. out-put units (for example As per track circuit power supplies to BR specifications no's. 927 and 929) since more economical smoothing arrangements may generally be obtained by incorporating smoothing stage in the equipment: itself.

Units with a current output rating of less than 10 A and units for use with high voltage point machines, see Appendix 4, may be housed during their service life in lineside apparatus cases. Units with a current output rating of 10 A and greater are generally housed in relay rooms.

Manufacturers shall ensure that the equipment complies with the relevant parts of the Health and Safety at Work Act 1974.

All units supplied to this specification shall have a minimum service life of 25 years.