EDIT Device Control 3 (Ctrl-S) This is one of four control codes meant to be used in controlling an auxiallary device.

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EDIT History On teletypes with paper tape punches, this control code turned off the paper tape punch so that subsequent characters would no longer be punched on the paper tape.

An older definition of this control code was XOFF (presumably Trasmit Off). This was sent to a host device when the client device (such as a teletype) was busy and unable to process any incoming characters. Once received by the host, it stopped transmitting data until a DC1 was received. This second usage is the one that survived the transition to video terminals.

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EDIT Modern Usage In most command line line interfaces, this character exhibits the XON behavior. At least one terminal emulator program interprets this character as a DC1 command, causing buffer capture to be turned off.

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EDIT Suggested Implementation A client device can send this control character if it will be unable to process further received characters. However this method of flow control is unreliable at higher data transmission rates, since, by the time the host has received the DC3, it may have already transmitted more characters.

It is recommended that client devices ignore this character, since factors such as line noise could cause a false DC3 to be received, resulting in the client appearing to be locked up since no correspinding DC1 will be received.

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