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PCE
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CPC Subgroup
H04M 1/20

Arrangements for preventing acoustic feed-back (H04M1/62 takes precedence)

Full Title

Substation equipment, e.g. for use by subscribers (subscriber services or facilities provided at exchanges H04M3/00; prepayment telephone coin boxes H04M17/00; current supply arrangements H04M19/08) > Constructional features of telephone sets > Arrangements for preventing acoustic feed-back (H04M1/62 takes precedence)