Introduction of pentaconta switching in paris

Describes the methods used for interconnection of older Rotary type telephone exchanges with the new Pentaconta (International Telephone and Telegraph automatic system based on crossbar switches) exchanges which are built now to meet the needs of the expanding network. The principles of the Rotary system are briefly explained and junction diagrams are shown for interconnections between Rotary and Pentaconta exchanges. Standard French code, called Socotel, is used for inter-exchange signalling; this is a seven-frequencies code, employing two-out-of-six frequencies for the digits and the seventh frequency for checking purposes. The signal flow is described for several combinations of interconnected exchanges. The operation of a very large Pentaconta exchange and the co-operation between old Rotary exchanges and their extensions in Pentaconta system are also discussed.