A method and apparatus are described for reframing a frame-structured telecommunication signal in which detection of a suspected misframe condition initiates a checking process to determine whether a misframe condition exists and at the same time initiates a hunting process to determine the correct frame structure. Checking is effected by accumulating indications of in frame and out of frame conditions in a bidirectional counter and an out of frame decision is made when the counter reaches a limit value. A local frame distributor is then shifted immediately to the new frame structure found by the hunting process. Reframing is thereby accomplished with minimal information loss.
A method of frame decoding a series data flow having a frame structure containing an item of periodically occurring synchronizing information, employs a frame recognition circuit, which is synchronized to the item of synchronizing information and is coupled to a frame generator. After a predetermined number of synchronous coincidences of the item of synchronizing information and a synchronizing signal emitted from the frame generator, the frame recognition circuit and frame generator are decoupled. During synchronous coincidence, a weighting counter is periodically increased by a predetermined amount, and in the case of non-coincidence it is periodically reduced by a predetermined amount. Resynchronization takes place only when the count of the weighting counter has reached its maximum value and the frame recognition circuit is synchronized to a new item of synchronizing information.
Circuit arrangement for synchronizing a subordinate system, in particular a digital subscriber station, by a superordinate system, in particular a digital exchange, in a PCM time-multiplex telecommunication network. The circuit arrangement operates to evaluate only those synchronization bit combinations which lie at the beginning of a message signal block, thereby avoiding initiation of a re-synchronization during transmission of a block.
An arrangement and method of aligning a digital transmission system receiver to an incoming redundant ternary line signal (6B4T code) which combines detection of an excessive number of code violations with detection of a large number of prohibited ternary words (i.e. redundant ternary words not allocated to a binary equivalent. This results in elimination of spurious realignments of the receiver coupled with rapid realignment when necessary with no disturbance to the output timing during realignment.
A process and apparatus for the synchronization on reception of a signal provided with a synchronization pattern. The process consists of retaining the synchronization setting until it can be readjusted on a periodically appearing potential synchronization pattern, optionally in the absence of a reference synchronization pattern corresponding to a previously acquired synchronization. The apparatus has a potential time base loaded to a given count during the presence of a potential synchronization pattern and a reference time base looped on itself and producing a synchronization signal when it reaches a given count. If a potential synchronization pattern is present in an iterative manner, a logic circuit produces a signal causing the synchronization change by loading the reference time base with the potential time base.
A receiver is disclosed which operates for synchronously receiving pulses of a serial stream without synchronizing the receiver clock to the clock at a transmitting site. Circuitry is provided for generating multiple delayed pulse signals in response to each incoming pulse and for sampling and maintaining a sequence of the most recent samples of the pulse signals. Decoding logic detects state transitions within the sequence, the location therein being indicative of the phase of the pulses relative to the clock signals. The decoding logic operates other circuitry for tracking the phase of the pulses as it drifts. The phase tracking circuitry enables the selection of ones of the samples which are synchronized, or in pulse durational phase, with the receiver clock for reconstructing the incoming pulse stream.
