Telegraphy the sense of a system that can transmit arbitrary messages over arbitrary distances. Lines of signalling relay stations can send messages to any required distance, but all these systems are limited to one extent or another in the range of messages that they can send. A system like flag semaphore, with an alphabetic code, can certainly send any given message, but the system is designed for short-range communication between two persons. An engine order telegraph, used to send instructions from the bridge of a ship to the engine room, fails to meet both criteria; it has a limited distance and
SPARS code SPARS code The SPARS code is a three-position alphabetic classification system developed in the early 1980s by the Society of Professional Audio Recording Services (SPARS) for commercial compact disc releases to denote aspects of the sound recording and reproduction process, distinguishing between the use of analog equipment and digital equipment. The code's three positions refer to recording, mixing, and mastering respectively. The first two positions may be coded either "A" for analog or "D" for digital; the third position (mastering) is always "D" on digital CDs. The scheme was not originally intended to be limited to use on digital packaged