In computer communications, enquiry is a transmission-control character that requests a response from the receiving station with which a connection has been set up. It represents a signal intended to trigger a response at the receiving end, to see if it is still present. The response, and answer-back code to the terminal that transmitted the WRU signal, may include station identification, the type of equipment in service, and the status of the remote station.
Some teleprinters had a "programmable" drum, which could encode 20 or 22 characters, programmable by breaking tabs off a drum. This sequence could be transmitted upon receipt of an enquiry signal, if enabled, or by pressing the "Here is" key on the keyboard.
DEC terminals respond to enquiry with the answerback message.
In some computer terminals and EMACS, it moves the cursor to the end of current line.
See also 
- ZDNet Definition for: Enquiry Character
- ATIS Telecom Glossary
- "ASR 33 Teletype Rear View of Main Assembly".
- "TELETYPE MODEL 32ASR".
- Browser Test Page for Unicode Character 'ENQUIRY' (U+0005)
- Enquiry Character from ComputerHope.com
- Enquiry character from SmartComputing.com