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Data Link

IP.com Disclosure Number: IPCOM000078590D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Kendrick, VC: AUTHOR [+2]

Abstract

A communication data link transfers audio communications or digital data by two identical circuits 10 and 11, one at each end of a line. Each circuit is a basic phase-locked loop. However, the voltage-controlled oscillator (VCO) 12 in each circuit is balanced at the input of their respective phase detectors 15, but is not balanced at their respective input ports 17 and 18. This allows each phase-locked loop to be insensitive to its own oscillator signal appearing at its own input and still be sensitive to all other signals. Consequently, oscillator 12 is connected to the input port so that VCO 12 signals will propagate down any line connected. Therefore, since there are two units, each will propagate a signal down the line.

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Data Link

A communication data link transfers audio communications or digital data by two identical circuits 10 and 11, one at each end of a line. Each circuit is a basic phase-locked loop. However, the voltage-controlled oscillator (VCO) 12 in each circuit is balanced at the input of their respective phase detectors 15, but is not balanced at their respective input ports 17 and 18. This allows each phase- locked loop to be insensitive to its own oscillator signal appearing at its own input and still be sensitive to all other signals. Consequently, oscillator 12 is connected to the input port so that VCO 12 signals will propagate down any line connected. Therefore, since there are two units, each will propagate a signal down the line.

When circuit 11 receives the oscillator signal from circuit 10, it phase locks to it because any signals besides the signal from its own oscillator appearing at ports 17 and 18 are not balanced out at the input of the phase detector. This unbalanced signal from detector 15 is passed through low-pass filter 16 to remove any noise.

If the filter 16 output differs from the original input IN to 11, comparator 14 provides an output and oscillator 12 will be synchronized via the analog OR. The same operation as above occurs when circuit 10 receives the oscillator signal from circuit 11. Consequently, both circuits are phased locked together. All that is required to transmit data is to change the level of the DC voltage at the input of either voltage-controlled oscillator, through its analog OR via either...