The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 11, 1997
Filed:
Jun. 12, 1995
James J Wisniewski, Bristow, VA (US);
Fred E Glave, Great Falls, VA (US);
Craig A Sharper, Los Altos, CA (US);
Hubbell Incorporated, Orange, CT (US);
Telesend, Inc., Los Altos, CA (US);
Abstract
An interface circuit is provided for implementing zero-byte substitution (ZBS) in a channel unit or line card which couples a digital subscriber line, such as a basic or primary rate Integrated Services Digital Network (ISDN) line, to a T1 network or other digital transmission facility. On the transmit side, the occurrence of an all-zero data byte in a B channel of the ISDN interface causes a corresponding zero byte indicator (ZBI) flag to be produced in the D+ channel, and also causes the all-zero byte to be replaced by the preceding non-zero data byte rather than by a prescribed or predetermined data byte. On the receive side, the occurrence of a repeated data byte in a B channel is detected and causes the current data byte to be replaced by an all-zero byte to restore the original data. The ZBI flag is then used as an error check bit to verify that the reinsertion of the all-zero byte was correct.