| 摘要 |
PURPOSE:To communicate a resending request signal to a transmission side device without fail even a long-distance line to which an echo suppressor is added by adding an attenuation function stopping signal in a transmission line besides the resending request signal when an error is detected at the received transmission signal. CONSTITUTION:When it is detected that image data PIX1 is an error, a command is issued from an error detecting terminal 24 to a resending request switch 410, a transmission/reception change-over switch 401 is thrown to a transmission side and a synthesizing signal of 350Hz and 2100Hz from a 350Hz oscillator 406 and a 2100Hz oscillator 407 or a sequential signal is sent. At this time, the suppression loss of an echo suppressor is removed, a level adjusting device 409 is prepared so that the echo suppressor can be always released without fail even when it is connected to any line of many and unspecified destinations and the area of a break-in W and a tone disabler circuit in the echo suppressor can be used together.
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