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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H04M1/738
Interface circuits for coupling substations to external telephone lines
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H04M1/74
with means for reducing interference; with means for reducing effects due to line faults
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H04M1/745
Protection devices or circuits for voltages surges on the line
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