FR2359554A1
Expired / Lapsed
FR
⏱️ 0.0 years remaining
Two condition telephone alarm system - employs low frequency carrier modulated with test frequency to indicate two possible alarm states
Assignee: Societe des Telephones Ericsson SA
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Filing: 1976-07-20
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Granted: —
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Expires: 1996-07-20
Abstract
Abstract A telephonic alarm system employs a signal of frequency fo modulated on a low frequency carrier fn and a line checking signal of frequency f1. All the signals are outside the frequency band employed for normal telephonic communications. A second level alarm is indicated by interruption of the modulation of fo which is detected by reception of the unmodulated fo signal and the fi signal. A first alarm condition is indicated by the absence of the fo signal component and the presence of the f1 component.
Inventors
- 👤 Maurice Adam
- 👤 Pierre Cleenewerck
Bibliographic Details
Application Number
—
Jurisdiction
FR
Data Source
google_patents
Last Synchronized
2026-11-05 08:16
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/04
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