OVERFORINGSANLEGGNING MED DIGITALA KANALER OCH EN DIGITAL SKYDDSKANAL

摘要

An errorless line protection switching system utilizes a variable delay (29) in the spare channel (21-24, 26-29, 31-33) adjusted to provide data signal alignment with an impaired regular channel before substituting the spare channel for the regular channel. This switching system is able to provide bit error free channel substitution between the spare and any regular channel in a digital radio system by virtue of the data signal alignment capability. Data signal alignment is provided by first aligning clocking signals in fine incremental steps with each clocking signal derived from one of the two channels undergoing the substitution. Data signal alignment is then provided by shifting the spare channel in full bit positions until data alignment is indicated by a detector (119). Data signal alignment is also utilized to restore service to a regular channel so the spare channel may be removed from service.