Patent classifications
H
ELECTRICITY
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H04
ELECTRIC COMMUNICATION TECHNIQUE
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H04M
TELEPHONIC COMMUNICATION
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19/00
Current supply arrangements for telephone systems
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H04M19/02
providing ringing current or supervisory tones, e.g. dialling tone or busy tone
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H04M19/04
the ringing-current being generated at the substations
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H04M19/047
Vibrating means for incoming calls
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