Baseband data switching apparatus for digital communications system

A baseband data switching apparatus for alternately switching between first and second channels, each channel having means for receiving baseband unipolar data and clock recovering means for recovering a clock from said baseband unipolar data, said switching apparatus comprising:

• first and second data phase adjusting means (301-303, 305) connected to the outputs of said receiving means and of said clock recovering means in said first and second channels, respectively, for adjusting the phase of said baseband unipolar data in each channel in a timed relationship with the respective recovered clocks;
• first and second clock phase adjusting means (304) respectively connected to the output of said clock recovering means in said first and second channels for respectively adjusting the phases of said recovered clocks;
• first (106) and second (206) unipolar/bipolar conversion means respectively connected to said first and second phase adjusting means and to said first and second clock phase adjusting means for respectively converting the phase-adjusted baseband unipolar data into bipolar data in response to a first control signal and to a second control signal, respectively;
• first (104) and second (204) frequency divider means respectively connected to said first and second clock phase adjusting means for respectively dividing the frequencies of the phase adjusted recovered clocks;
• first (105) and second (205) control signal supply means for respectively and selectively reversing the polarities of the outputs of said first and second frequency divider means in response to respective third and fourth control signals to provide said first and second control signals;
• coincidence detecting means for detecting coincidence or non-coincidence between the outputs from said first and second unipolar/bipolar conversion means, said third and fourth control signals being produced in response to an output from said coincidence detecting means such that said third and fourth control signals have polarities which cause the polarities of said outputs from said first and second unipolar/bipolar conversion means to be coincident;
• and
• means for switching between the outputs of said first and second unipolar/bipolar conversion means.