| 摘要 |
PURPOSE:To realize a titled interphone which can receive the carrier signal from the other station without receiving any interference from the carrier signal of own station, by constituting an arrangement so that the carrier signals of own station and the other station are mixed in the receiving system and only the difference between both carrier signals or the sum of both carrier signals is passed. CONSTITUTION:An interphone transmitting system contains a microphone M, a preamplifier 3 of sound signals converted into electric signals by the microphone, a modulator 4 which modulates carrier signals f1 by using the amplified sound signals, and a high-frequency power amplifier 5 which performs power amplification on the modulated carrier signals. On the other hand, the receiving system contains a mixer 6 which mixes the carrier signal f1 of own station and the carrier signal f2 from the other stationI2 with each other, a BPF7 which passes only the difference between both carrier signals,¦f1-f2¦, or the sum of both signals f1+f2, a demodulator 8 which demodulates the sending signal from the other stationI2 which is modulated to the difference or sum signal, a power amplifier 9 which performs power amplification on the demodulated received signal, and a speaker SP of a handset 2 which performs electric-acoustic conversion on the power-amplified sound signals. |
