Arrangements for signalling the number or class of the calling line to the operator (between operators in inter- exchange working H04M5/18)

Full Title

Automatic or semi-automatic exchanges > Semi-automatic systems, i.e. in which the numerical selection of the outgoing line is under the control of an operator > Arrangements for signalling the number or class of the calling line to the operator (between operators in inter- exchange working H04M5/18)