Arrangements for interconnection between switching centres

Classification Context

Section:

ELECTRICITY

Class:

ELECTRIC COMMUNICATION TECHNIQUE

Subclass:

TELEPHONIC COMMUNICATION

Child Classifications

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• H04M 7/02 for compensating differences of ground potential
• H04M 7/04 for compensating differences of line impedance
• H04M 7/06 using auxiliary connections for control or supervision
• H04M 7/08 for phantom working
• H04M 7/1 for two-way working, i.e. calls may be set-up in either direction over the same connection
• H04M 7/12 for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal
• H04M 7/14 in systems involving main and subordinate switching centres
• H04M 7/16 in systems employing carrier frequencies