Remote master/slave station clock
AssigneeDigital Communications Corporation
InventorsOva Gene Gabbard, Pradeep Kaul, Joaquin Hangen
Life of this patent
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Abstract
A clock for locally distributing a synchronized signal derived from a remotely transmitted signal. The clock normally operates in the slave mode, phase locked to the remotely transmitted signal, when that signal is deemed available. If it is not available the clock switches to a master mode in which it independently generates the necessary signal.
Claims12
A phase lock loop for generating a stable reconditioned signal in response to a remotely transmitted signal and for independently producing said signal when said remotely transmitted signal is unavailable, comprising;
- an input port responsive to said remotely transmitted signal and having serially connected thereto,
- a phase detector,
- a low pass filter,
- an analog to digital convertor,
- a multiplexer,
- a digital to analog convertor, and to a voltage controlled oscillator, said voltage controlled oscillator providing a second input to said phase detector,
- memory means, including filter means, serially connected between said analog to digital convertor and said multiplexer for storing a filtered digital representation of the output of said analog to digital convertor,
- means for detecting unavailability of said remotely transmitted signal, and
- switch means responsive to detected failure of said remotely transmitted signal for controlling said multiplexer to be responsive only to said memory means.
Synchronized Master/Slave clock for locally distributing, from an output port, a stable reconditioned signal synchronized with a remotely transmitted signal and also capable of independently producing said signal when said remotely transmitted signal is unavailable, comprising;
- a. at least three timing generator means, each of said timing generator means including,
- i. a phase lock loop responsive to said remotely transmitted signal for producing said stable reconditioned signal,
- ii. memory means, including filter means, connected to said phase lock loop retaining a quantity indicative of the frequency generated thereby,
- iii. loop switch means for opening said phase lock loop and connecting said memory means to control said loop oscillator,
- iv. means for detecting unavailability of said remotely transmitted signal and for producing a signal indicative thereof, and
- v. means for detecting failure of said phase lock loop and for producing a signal indicative thereof,
- b. switch means selectively connecting said stable reconditioned signals to said output port,
- c. majority voting logic means responsive to said plurality of failure indicating signals and connected to said switch means for selectively controlling said switch means to connect one or more of said stable reconditioned signals to said output port, said majority voting logic means also connected to said loop switch means and responsive to signals indicative of failure of said remotely transmitted signal for operating said loop switch means.
Dependencies are inferred from the claim text.