Zero-Bit Insertion

What Does Zero-Bit Insertion Mean?

Zero-bit insertion is a bit-stuffing technique in which a zero bit is inserted after a series of one bits to highlight a sequence change or break. Zero-bit insertion is used with other bit-oriented protocols to prevent the accidental appearance of six consecutive one bits between the two framing flags indicating a transmission frame’s beginning and end.

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Techopedia Explains Zero-Bit Insertion

Zero-bit transmission is widely used in IBM’s High-Level Data Link Control (HDLC) – a data link format structure. The HDLC format requires that a frame’s beginning and end be flagged. Zero-bit insertion is generally used to distinguish between the flag pattern and data of the same format. The flag byte normally contains the bit sequence “01111110.”

To keep the flag byte bit sequence from occurring within the transmission frame, the HDLC transmitter inserts a zero after five consecutive bits. The only drawback of the zero-bit insertion technique is its irregular code or information rate.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.