| 摘要 |
An improved Range Extender with Gain (REG) comprises a floating loop current detector, a new dial pulse reshaper and a new control logic circuit. The loop current detector is powered by means of a floating power supply which renders the detector insensitive to spurious common-mode subscriber loop currents. The dial pulse reshaper comprises logic gates with two feedback paths for regenerating minimum make and break periods. The control logic circuit for controlling the relays in the REG is an asynchronous logic circuit particularly designed to avoid conventional differentiation circuits and timing problems associated with Automatic Number Identification.
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