| 摘要 |
The device is intended to amplify earpiece signals in a handset of a telephone for the hard of hearing, with adjustable gain by potentiometer 12. The device DA can be interconnected within an earpiece signal reception path VR and a microphone signal transmission path VM between the base and the handset of the set, without requiring any modification of the set. It comprises a detector 2 of microphone voltages greater than a predetermined threshold in the transmission path VM, and a control circuit 4 with relay 3 with two contacts 31, 32, connected to the detector so as simultaneously to power an amplifying circuit 1 via a self-contained voltage source 5 and to interconnect the amplifying circuit into the reception path VR only in response to microphone voltages greater than the predetermined threshold following the lifting of the handset. When the handset is hung up, the amplifying circuit is not powered. <IMAGE>
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