Patent classifications
H
ELECTRICITY
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H04
ELECTRIC COMMUNICATION TECHNIQUE
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H04M
TELEPHONIC COMMUNICATION
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9/00
Arrangements for interconnection not involving centralised switching
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H04M9/002
with subscriber controlled access to a line, i.e. key telephone systems
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H04M9/003
Transmission of control signals from or to the key telephone set; signalling equipment at key telephone set, e.g. keyboard or display equipment
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