Communication speed switching device

摘要

It is decided whether or not the reception is performed with respect to signals of 1650Hz, 1750Hz and 1850Hz passed through band pass filter (BPF) 4031 up to 4033 and processed for the energy calculation in energy calculating circuit 4041 up to 4043 respectively. Low speed signals that are processed for the energy calculation in energy calculation circuit 4041 up to 4043 respectively are added in adding section 405. At this time, a timer in decision circuit 406 starts. When a predetermined time passes in the timer in decision circuit 406 with a predetermined energy level of signals of 1650Hz, 1750Hz and 1850Hz kept, the signals are identified as EOP signal that comes after PIX signal. Thereby the apparatus is controlled to shift to the low speed signal reception mode.