COMMUNICATION METHOD AND APPARATUS

摘要

A method of transmitting secondary data (63) over a communications link (44, 45, 46) which transmits blocks of primary data (57) in a data stream between a sending station (43, 47, 52) and a receiving station (43, 47, 52). Secondary data (63) is formatted according to a protocol other than that used to format the primary data and is inserted between the blocks of primary data. At a receiving station (43, 47, 52) the secondary data is extracted and the data stream is reinstated to its original form. An apparatus for effecting the method includes interface ports (70, 71) and a first in/first out interface (73) interconnected via a cross connect switch (72). A CPU (74) provides secondary data to the first in/first out interface to be inserted between blocks of primary data and routed via cross connect switch (72) to an interface port (70, 71). A watchdog means (75) monitors the CPU and controls the cross connect switch (72) to effect a direct connection between the interface ports (70, 71) if the CPU is inactive.