| 摘要 |
PROBLEM TO BE SOLVED: To unnecessitate a voice input by a resident in a dwelling unit and to easily monitor a security state near the entrance of the dwelling unit. SOLUTION: When the handset 25 of an indoor master unit 2 in waiting state is picked up, a speech communication circuit 27 and a tone-for-learning generation circuit 29 are activated due to the control of a controller 20 detecting a hook switch 26 that has been subjected to off-hook, and an analog switch 30 for learning is also closed. The sound pressure level of a sound for learning signal S31 from the circuit 29 is detected by the sound echo canceler 16 of an entrance slave unit 1 through a transmission line L1 and the signal S31 is outputted as sound for learning from a loud speaker 13. The sound echo canceler also generates a pseudo-echo signal from an echo feedback sound for learning signal S41 obtained by adding a direct wave and a reflected wave to sound for learning picked up by a slave unit microphone 12 and the sound for learning signal, subtracts the finite difference of a pseudo-echo signal from the sum signal of a monitor echo signal S42 near the dwelling unit entrance and the echo feedback sound for learning signal, and monitored sound whose sound echo component is attenuated is outputted from a receiver 25 constituting a handset.
|
