CIRCUIT ARRANGEMENT FOR A CALL, DOOR INTERCOM AND DOOR OPENER SYSTEM
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CIRCUIT ARRANGEMENT FOR A CALL, DOOR CHANGER AND DOOR OPENING SYSTEM
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CIRCUIT ARRANGEMENT FOR A CALL, DOOR CHANGER AND DOOR OPENING SYSTEM
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Intercommunication and door opener system - is for blocks of flats and has logic suppressing door opener when call button is pressed
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DEVICE FOR PROTECTING THE ELECTRONIC IMAGE DISASSEMBLER OF A TELEVISION CAMERA FROM OPTICAL DAMAGE
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CIRCUIT ARRANGEMENT FOR DOOR INTERCOM SYSTEMS WITH INDEPENDENT, VOICE-CONTROLLED INTERCOM OR SEMI-DUPLEX AMPLIFIER
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Power rectifier, especially for in-house telephone systems
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Intercom with several door intercoms and internal intercoms
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Attachment of the connecting cord to a telephone handset
DE1566743B1
Circuit arrangement for call devices of door intercoms
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Call circuit arrangement for door intercom with several apartment intercoms
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Telephone facility
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Intercom for two-way or two-way communication with call facility
DE838619C
Circuit arrangement for combined door and house telephone systems
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Circuit arrangement for door loudspeaker systems
DE455214C
Circuit arrangement for telephone exchanges with two-part pair of cords and devices which cause the interrogator to switch off automatically to maintain confidentiality
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Listening device for over and talk measurements using a comparison line
