of the same line (carriage return), advance to the same column of the next line (line feed), and so on. Commands to control non-printing operations were transmitted in exactly the same way as printable characters by sending control characters with defined functions (e.g., the line feed character forced the carriage to move to the same position on the next line) to teleprinters. In modern computing and communications a few control characters, such as carriage return and line feed, have retained their original functions (although they are often implemented in software rather than activating electromechanical mechanisms to move a physical printer carriage) but many others are no longer required and are used for other purposes. 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 ENQ (control E) signal, if enabled. 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?" Manufacturers Creed & Company British Creed & Company built teleprinters for the GPO's teleprinter service. Creed model 7 (page printing teleprinter introduced in 1931) Creed model 7B (50 baud page printing teleprinter) Creed model 7E (page printing teleprinter with overlap cam and range finder) Creed model 7/TR (non-printing teleprinter reperforator) Creed model 54 (page printing teleprinter introduced in 1954) Creed model 75 (page printing teleprinter introduced in 1958) Creed model 85 (printing reperforator introduced in 1948) Creed model 86 (printing reperforator using 7/8" wide tape) Creed model 444 (page printing teleprinter introduced in 1966, GPO type 15) Gretag The Gretag ETK-47 teleprinter developed in Switzerland by Edgar Gretener in 1947 uses a 14-bit start-stop transmission method similar to the 5-bit code used by other teleprinters. However, instead of a more-or-less arbitrary mapping between 5-bit codes and letters in the Latin alphabet, all characters (letters, digits, and punctuation) printed by the ETK are built from 14 basic elements on a print head, very similar to the 14 elements on a modern fourteen-segment display, each one selected independently by one of the 14 bits during transmission. Because it does not use a fixed character set, but instead builds up characters from smaller elements,