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G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
G08B7/00—Signalling systems according to two or more of groups G08B3/00 - G08B6/00
G08B7/06—Signalling systems according to two or more of groups G08B3/00 - G08B6/00 using electric transmission, e.g. involving audible and visible signalling through the use of sound and light sources
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FR538486D1921-07-191921-07-19Perfectionnements apportés aux signaux lumineux électriques
ExpiredFR538486A
(fr)