| 摘要 |
PROBLEM TO BE SOLVED: To improve reception sensitivity of a multiple dwelling house intercom system.SOLUTION: A multiple dwelling house intercom system includes a branching device 4a, 4b comprising: an upstream side branching device I/F 40 for withdrawing an upstream side dwelling unit line L2; a downstream side branching device I/F 41 for withdrawing a downstream side dwelling unit line L2; a signal branching transmission/reception section 42 having a function for transmitting an up transmission signal from an own dwelling unit from the upstream side branching device I/F 40 as well as transmitting a down transmission signal from the upstream side branching device I/F 40 to the own dwelling unit side, and a function for transferring a down transmission signal from the upstream side branching device I/F 40 to the downstream side and an up transmission signal from the downstream side branching device I/F 41 to the upstream side; a first down transmission filter 44 for passing only a frequency band of the down transmission signal from an output signal of the signal branching transmission/reception section 42; an up transmission filter 48 for passing only a frequency band of the up transmission signal from the own dwelling unit; and an up transmission amplifier 47 for amplifying the up transmission signal to transmitting it to the signal branching transmission/reception section 42. |
