Spurious Interrupts Releases prior to 3.3: Spurious interrupt means that CTS, DSR, and/or DCD startled toggling (low to high, over and over) more than 10,000 times in a one second window. Any of these signals toggling like this will cause a Spurious Interrupt. Release 3.3 and up: Serial port spurious interrupt handling has been extended to include detecting streams of framing errors. Some modems get confused about their configuration and begin sending continuous data to the PortMaster at a baud rate different than set on the PortMaster. This would cause all operation on the PortMaster to appear stopped for several minutes to several hours. The PortMaster now attempts to reset the modem and will continue to operate properly even if the modem does not recover.