X-ON/X-OFF

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X-ON/X-OFF A method of flow-control based on the exchange of specific control characters over a duplex channel. The sending device will assume that the receiver is able to accept characters at any time, and will transmit on that basis. If the receiver is unable to accept further characters it will transmit an `X-OFF' character to the sender, which must then cease transmission until an `X-ON' character is transmitted by the receiver.