Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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International Standard Electric Corp
Original Assignee
International Standard Electric Corp
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Filing date
Publication date
Application filed by International Standard Electric Corp filedCriticalInternational Standard Electric Corp
Publication of FR2176144A1publicationCriticalpatent/FR2176144A1/fr
H04M1/00—Substation equipment, e.g. for use by subscribers
H04M1/26—Devices for calling a subscriber
H04M1/515—Devices for calling a subscriber by generating or selecting signals other than trains of pulses of similar shape, or signals other than currents of one or more different frequencies, e.g. generation of DC signals of alternating polarity, coded pulses or impedance dialling