Editing Teleprinter (section)

===Answer back mechanism===
Some teleprinters had a "Here is" key, which transmitted a fixed sequence of 20 or 22 characters, programmable by breaking tabs off a drum. This sequence could also be transmitted automatically upon receipt of an [[Enquiry character|ENQ]] (control E) signal, if enabled.<ref name="Hereis">{{Cite web |url=http://www.pdp8online.com/asr33/pics/main_back.shtml |title=ASR 33 Teletype Rear View of Main Assembly |website=www.pdp8online.com}}</ref><ref name="AnotherHereis">{{Cite web |url=http://www.k7tty.com/development/teletype/model-32/index.html |title=TELETYPE MODEL 32ASR. |website=www.k7tty.com}}</ref> This was commonly used to identify a station; the operator could press the key to send the station identifier to the other end, or the remote station could trigger its transmission by sending the ENQ character, essentially asking "who are you?"