Asynchronous Terminals and Printer Processes Programming Manual

TERMINAL PROGRAMMING CONSIDERATIONS
Modem Error
retrying the READ, you should send a message to the terminal
operator instructing him to reenter the most recent data string.
Modem Error
Error 140 occurs if the carrier signal to the modem is lost in
half-duplex operation or if DSR is lost in switched operation.
The signal loss can be either momentary or permanent. In
either case, assume that data was lost. The first time error
140 occurs, send a retry message to the terminal operator (if
reading) before retrying the operation. If error 140 occurs
on the retry, the connection with the remote terminal is lost.
When the second error occurs, call the CONTROL procedure to
disconnect the modem and then call CONTROL again to establish
another connection.
Path Errors
The path errors (errors 200-255) should be handled as described
in the "File-System Errors" section of the System Messages
Manual .
If any one of errors 210 through 231 occurs, the operation failed
at some indeterminate point. If reading, send a retry message to
the terminal operator before retrying the read.
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