Browse Prior Art Database

Encoder for a Bipolar 8 Zero Substitution (b8zs) Code On a T1 Line

IP.com Disclosure Number: IPCOM000041071D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Anderson, RB: AUTHOR

Abstract

In T1 lines, local clocks must be synchronized by receiving a binary one transition at least once during every eight-bit interval. Therefore, any binary sequence containing more than eight consecutive zeros must be modified in order to maintain the local clocks in synchronization. The T1 lines have a convention that binary one bits are represented by a pulse on the line and binary zero bits are represented by the absence of a pulse on a line. Consecutive pulses must be of the opposite polarity on the line. The problem of preventing the occurrence of eight consecutive bit intervals occurring with the absence of pulses which could resynchronize the clocks has been solved in the prior art by the "bipolar with 8 zero substitution" (B8ZS) convention for T1 lines.

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Encoder for a Bipolar 8 Zero Substitution (b8zs) Code On a T1 Line

In T1 lines, local clocks must be synchronized by receiving a binary one transition at least once during every eight-bit interval. Therefore, any binary sequence containing more than eight consecutive zeros must be modified in order to maintain the local clocks in synchronization. The T1 lines have a convention that binary one bits are represented by a pulse on the line and binary zero bits are represented by the absence of a pulse on a line. Consecutive pulses must be of the opposite polarity on the line. The problem of preventing the occurrence of eight consecutive bit intervals occurring with the absence of pulses which could resynchronize the clocks has been solved in the prior art by the "bipolar with 8 zero substitution" (B8ZS) convention for T1 lines. If eight consecutive zero bits must be transmitted in the data traffic, an intentionally illegal configuration of two consecutive pulses of the same polarity are applied to the T1 line, signifying that a sequence of eight binary zeros should be inferred. This will become a convention employed for all T1 lines.

The invention disclosed herein is an embodiment of a B8ZS encoder in the form of a programmable logic sequencer which is connected to an input data stream to be encoded. The programmable logic sequencer, shown schematically in Fig. 1, is programmed with the encoder state diagram shown in Fig. 2, so as to carry out a sequence of operating...