Patent classifications
H
ELECTRICITY
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H04
ELECTRIC COMMUNICATION TECHNIQUE
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H04M
TELEPHONIC COMMUNICATION
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3/00
Automatic or semi-automatic exchanges
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H04M3/42
Systems providing special services or facilities to subscribers
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H04M3/56
Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities
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H04M3/563
User guidance or feature selection
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H04M3/564
whereby the feature is a sub-conference
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