Phase-locked loop and clock circuit for a line switch
First Claim
1. A circuit arrangement responsive to an input signal of a first frequency at a first terminal for generating output signals of a second frequency and having a predetermined phase relationship to said input signals at a second terminal, said circuit arrangement comprising:
- a voltage controlled oscillator having an output coupled to said second terminal and having a control input, said voltage controlled oscillator generating a signal having a frequency dependent on the voltage level at said control input;
means coupled to said voltage controlled oscillator output for supplying feedback signals; and
first means responsive to said input signals and said feedback signals for supplying said voltage level, said first means comprising;
a controlled voltage source for generating said voltage level in response to first and second control signals, said controlled voltage source being responsive to said first control signal to change said voltage level in a first direction and being responsive to said second control signal to change said voltage level in a second direction opposite said first direction; and
detection means for generating said first and second control signals in response to said input signals and said feedback signals, said detection means having a first stable state whereby neither said first nor said second control signals are generated, a second stable state whereby only said first control signal is generated, and a third stable state whereby said second control signal is generated, said detection means normally being in said first stable state, said detection means assuming said second stable state each time said input signal occurs prior to said feedback signal and remaining in said second stable state for substantially the time difference between the occurrences of said input signal and said feedback signal, said detection means returning to said first stable state from said second stable state after the occurrence of said feedback signal, said detection means assuming said third stable state each time said feedback signal occurs prior to said input signal and remaining in said third stable state for substantially the time difference between the occurrence of said feedback signal and said input signal, said detector means returning to said first stable state from said second stable state after the occurrence of said input signal.
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Accused Products
Abstract
A line switch for a digital telephone switching system utilizes distributed processing. The line switch comprises one or more switch modules. Each switch module is coupled to a central office switching system via one or more PCM lines which utilize common channel signaling. Each switch module comprises groups of line circuits, each line circuit being coupled to a subscriber line. Three separate distributed processor functions are provided in each line switch module. First one processor is utilized to communicate with the central office switching system and to coordinate the operations within the line switch module. A second processor is provided to control clock generation and rate conversion circuits. Each group of line circuits includes a third processor to control the operations of the line circuits and to gather information from the line circuit.
The second processor is used to select which of a plurality of sources may be used to provide clock signals within the line switch module.
A phase-locked loop permits clock signals which are generated in a line switch module to be in phase synchronism with any one of the PCM lines. When two or more lines switch modules are connected together to form a line switch, the phase-locked loop circuits of each module will utilize the same PCM line for phase-locking.
18 Citations
21 Claims
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1. A circuit arrangement responsive to an input signal of a first frequency at a first terminal for generating output signals of a second frequency and having a predetermined phase relationship to said input signals at a second terminal, said circuit arrangement comprising:
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a voltage controlled oscillator having an output coupled to said second terminal and having a control input, said voltage controlled oscillator generating a signal having a frequency dependent on the voltage level at said control input; means coupled to said voltage controlled oscillator output for supplying feedback signals; and first means responsive to said input signals and said feedback signals for supplying said voltage level, said first means comprising; a controlled voltage source for generating said voltage level in response to first and second control signals, said controlled voltage source being responsive to said first control signal to change said voltage level in a first direction and being responsive to said second control signal to change said voltage level in a second direction opposite said first direction; and detection means for generating said first and second control signals in response to said input signals and said feedback signals, said detection means having a first stable state whereby neither said first nor said second control signals are generated, a second stable state whereby only said first control signal is generated, and a third stable state whereby said second control signal is generated, said detection means normally being in said first stable state, said detection means assuming said second stable state each time said input signal occurs prior to said feedback signal and remaining in said second stable state for substantially the time difference between the occurrences of said input signal and said feedback signal, said detection means returning to said first stable state from said second stable state after the occurrence of said feedback signal, said detection means assuming said third stable state each time said feedback signal occurs prior to said input signal and remaining in said third stable state for substantially the time difference between the occurrence of said feedback signal and said input signal, said detector means returning to said first stable state from said second stable state after the occurrence of said input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A circuit arrangement responsive to input signals of a first frequency for generating at an output terminal output signals of a second frequency having a predetermined phase relationship to said input signals, said circuit arrangement comprising:
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a voltage controlled oscillator having a voltage control input and an output coupled to said output terminal; means coupled to said voltage controlled oscillator output for providing a feedback signal; a detection circuit comprising first bistable means having first and second conductive states and being responsive to the occurrence of said input signal for switching from said first conductive state to said second conductive state, and second bistable means having first and second conductive states and being responsive to the occurrence of said feedback signals for switching from said first conductive state to said second conductive state, and reset means for resetting said first and second bistable means to said first conductive state after said first and second bistable means are both switched to said second state; and voltage control means for generating a control voltage at said voltage control input, said voltage control means comprising first means for increasing the voltage level of said control voltage in response to one of said first and second bistable means having said second conductive state and for decreasing the voltage level of said control voltage in response to the other one of said first and second bistable means having said second conductive state. - View Dependent Claims (10, 11, 12, 13)
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14. A circuit for receiving at an input terminal PCM framing clock pulses at one frequency and for generating at an output terminal second PCM bit clock pulses at a second frequency, said circuit comprising:
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voltage controller oscillator means having an output coupled to said output terminal and a control input, said voltage controlled oscillator means generating said second PCM bit clock pulses at a frequency dependent on the voltage level at said control input; feedback means coupled to said oscillator means output for dividing the frequency of said second PCM bit clock pulses by a predetermined factor to generate feedback clock pulses; phase detector means for generating error current when said feedback clock pulses are out of phase with said framing clock pulses; loop filter means for integrating said error currents to generate said voltage level; and means for deriving said PCM framing clock pulses from first PCM bit clock pulses. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification