| 摘要 |
PURPOSE:To make it possible to perform operation based upon the advice of CCITT without reference to the time when a received carrier is being cut off by detecting whether a synchronizing signal has been received from a received waveform and then by controlling a received carrier detecting circuit according to the degree of the convergence of an automatic automatic equalizer in case of instataneous breaking. CONSTITUTION:Input signal A is applied to reception level deciding circuit 1 having hysteresis characteristics and synchronizing signal detecting circuit 3. When input signal A is at a low level and deciding circuit 1 is OFF, its output is supplied to timer 2 and after its time limit, the received-carrier detecting circuit is turned off. As deciding circuit 1 turns on, detecting circuit 3 is enabled to detect a synchronizing signal. The output of detecting circuit 3 is led to the control input terminal of selector 4 and when the synchronizing signal is received, deciding circuit 5 turns on before user's data are outputted to make sure of synchronism with the reception part. Once the received carrier is instantaneously cut off, signal quality detecting circuit 6 outputs a high-level signal and RSFF7 is set, so that its output B will be turned on. |
