Patent classifications
H
ELECTRICITY
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H04
ELECTRIC COMMUNICATION TECHNIQUE
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H04M
TELEPHONIC COMMUNICATION
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Substation equipment, e.g. for use by subscribers
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H04M1/02
Constructional features of telephone sets
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H04M1/21
Combinations with auxiliary equipment, e.g. with clocks or memoranda pads
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H04M1/215
by non-intrusive coupling means, e.g. acoustic couplers
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