| 摘要 |
A selective ringing receiving circuit comprises a timing generating circuit for generating a timing signal for bit length comparison, a bit length comparison circuit for comparing, in terms of the timing signal, the respective bit lengths of '1' and '0' of a received digital signal outputted in a direct conversion system when a selective ringing signal is received from a base station, thereby producing a changing point detection/selection signal, a changing point detection circuit for selecting the rising and falling changing points of the received signal using the changing point detection/selection signal to produce a detected rising or falling changing point signal of the received digital signal, and a bit synchronization circuit for performing bit synchronization in response to the detected changing point inputted. Thus, even if the outputting frequency of the receiving station or the transmission frequency in the base station fluctuates, normal bit synchronization for the received digital signal can be made.
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