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
Japanese cryptology from the 1500s to Meiji system in World War I were chosen because in morse code they are quite distinct and thus it was unlikely that an error in the morse code transmission would accidentally turn one letter into another. This would have been important for a sengoku daimyō, for instance, if he experimented with sending coded messages over long distances by torches, flags, poles, or similar system. Finally, although the checkerboard system doubles the length of messages, breaking each plaintext letter into two ciphertext letters allows for separate transformations on each of the halves. However, this does not seem to have been used much