IPC Main Group
H04M 7/00 Arrangements for interconnection between switching centres
Introduced: September 1968
Last revised: January 2006
Classification Context
- Section:
- ELECTRICITY
- Class:
- ELECTRIC COMMUNICATION TECHNIQUE
- Subclass:
- TELEPHONIC COMMUNICATION
8 direct subcodes
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