Monitor system for atm cross connect device

PURPOSE:To easily detects an error in a monitor cell by setting a PN pattern prescribed value and a PN pattern based thereon to an information field of the monitor cell. CONSTITUTION:When a monitor cell is outputted through an ATM cross connector 1, an error check section 3 detects a prescribed value of a PN pattern in an information field PL of a cell format and a PN pattern and compares the detected PN pattern with the PN pattern based on the prescribed value to implement error monitor of a path in the connector 1. Thus, whether or not a path in the connector is normal is easily discriminated at an output of the connector 1 based on a change in the PN pattern or a VPI(virtual path identifier).