Abstract: An ATM transmission system transmits cell-formatted data in an asynchronous transfer mode, and aims at conducting an online path route test in the system. If one path route only is established in the system, then one or more valid cell detecting units for detecting, upon receipt of a cell enable signal indicating that a valid cell to pass through the path route has been sent, the arrival of a valid cell are provided at an optional point including an ATM switch in the path route so that the path route can be partially or entirely validity-checked. If plurality of valid path routes are established, the system provides, in addition to the valid cell detecting units, a virtual path identifier and virtual channel identifier comparing unit for comparing values of the VPI and VCI stored therein with values of a VPI and a VCI added to an arriving cell, and a path route validity check unit for partially or entirely validity-checking a path route in the ATM transmission system.

Abstract: A CRC operating unit which performs a CRC operation on received data using as an initial value a CRC operation result actual value obtained in a previous operation, and outputs a CRC operation result actual value. A delay unit delays the CRC operation result actual value by the time taken for a header part to be entered. The CRC operation result derivation unit outputs as a CRC operation result derivation value an operation result obtained by a CRC operation performed for all the receiving data of a header part provided with the above described CRC code using the CRC operation result actual value as an initial value. The coincidence detecting unit compares the CRC operation result actual value with the CRC operation result derivation value to detect the input timing of a header part as coincident timing for both values.

Abstract: In a control system for switching between a first system and a second system of a duplicated selecting structure in an ATM exchange, one of the first and second systems operates as an active system, and the other operates as a standby system. A generator unit writes specific bits into ATM cells received via an input transmission line. The specific bits respectively written into ATM cells to be transferred via the active system indicate a first state, and those respectively written into the ATM cells to be transferred via the standby system indicate a second state. A first table stores the specific bits respectively assigned to VPI/VCI pairs related to the ATM cells transferred via the first system. A second table stores the specific bits respectively assigned to VPI/VCI pairs related to the ATM cells transferred via the second system.

Abstract: An in-service activator for a broadband exchanger has a dual system structure, in which a first system and a second system form a dual pair. The first system and the second system in the dual pair each has at least one [1] channel converter and a switcher. A channel converter stores channel setting information for use in routing a cell inputted from a line, and outputs the cell inputted from the line by attaching the channel setting information to the cell. The switcher switches a cell outputted from a channel converter. The interfacer stores, in a channel converter of a to-be-activated standby system in the dual pair, the channel setting information read from the corresponding channel converter of an act system in the duplex pair.