Two polarised relays used on D.C. selective ringing telephone omnibus circuit, Newport station exchange Two polarised relays used on D.C. selective ringing telephone omnibus circuit
Two polarised relays 4500/4500 used on 4-button selective omnibus circuits, Newport station exchange Two polarised relays 4500/4500 used on 4-button selective omnibus circuits
Two polarised relays 10000/10000: (a) used on railway control telephone system; (b) used on railway selective circuits - from Newport station exchange Two polarised relays 10000/10000