Return messages on physical consoles

NBC0050	CONSOLE ERROR - TRY AGAIN appears if an error occurred during reading.
NBC0051	TIMEOUT - INPUT IGNORED appears if the previous input operation was aborted by the software because of an error.
NBC0052	INPUT NULL - IGNORED appears when the operator has entered only END OF TEXT.
NBC0053	RECIPIENT NOT AVAILABLE - INPUT IGNORED appears if an entry cannot be forwarded to the recipient because the recipient is not available.
NBC0054	UCON NOT ACTIVE - INPUT IGNORED appears if entries not beginning with P. were made between the time when IPL was terminated and UCON was started.
NBC0055	INVALID PREFIX ENTERED - NO SUCH ANSWER EXPECTED appears if an entry beginning with P. or E. was made although no query with one of these prefixes is open.
NBC0058	UCON BUSY - INPUT IGNORED appears if an entry could not be passed as a result of UCON problems.
NBC0059	NO PF1-, PF2- OR ENTER-KEY USED - INPUT IGNORED appears if an entry was not terminated with the PF1, PF2 or ENTER key.
NBC0070	CIO TESTS THIS CONSOLE appears after the system has recovered from a situation in which no operable console was available. If all consoles are defective, they are tested cyclically with this message. The first operational console found outputs this message.