Browse Prior Art Database

Bipolar PCM Transparency

IP.com Disclosure Number: IPCOM000091413D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Croisoer, A: AUTHOR

Abstract

In bipolar coding, each input binary digit is translated into a three-level signal. According to coding method, no pulse represents a binary 0. A 1 is represented by a positive or a negative pulse. Furthermore, two successive. 1's are always of opposite polarities irrespective of the number of 0's separating them. Conventional bipolar coding is not transparent to clock signals. That is, synchronization cannot be derived from the coded data entering the receiver station, since, in the case of a long string of 0's, no significant information is received.

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Bipolar PCM Transparency

In bipolar coding, each input binary digit is translated into a three-level signal. According to coding method, no pulse represents a binary 0. A 1 is represented by a positive or a negative pulse. Furthermore, two successive. 1's are always of opposite polarities irrespective of the number of 0's separating them. Conventional bipolar coding is not transparent to clock signals. That is, synchronization cannot be derived from the coded data entering the receiver station, since, in the case of a long string of 0's, no significant information is received.

In order to make bipolar coding transparent, a specific pattern of bits of information is added, at a location in the message where, due to the lack of nonzero bits, clock pulses cannot be recovered from such information. In this system, bipolar violations are no longer avoided and, contrarily, are used for the purpose of transparency of received information. If a string of 0's exceeds five bits, it is filled partially with a pattern of an even number of successive 1's. The first 1 of such pattern is in bipolar violation with the last transmitted 1 pertaining to the coded information.

The desired bipolar violation is distinguished from the one regulating from noise on the line or from faulty operation of the transmitter by a special additional rule. A predetermined sequence of bits is used between the last 1 of the coded information and the first 1 of such pattern. For identical purposes, a...