In 1963, details were published of a new method of teleprinter signalling for use on high-frequency radio circuits. This system (Piccolo) uses a different tone to represent each of the 32 characters of the teleprinter alphabet; the tones are orthogonally related and are detected at the receiver by quenched resonators. Piccolo has been further developed and refined, and has been adopted by the British Foreign & Commonwealth Office as the standard machine-telegraph method for diplomatic wireless communications; it is now in worldwide use. The paper describes the improvements made to the original models, a range of new ancillaries to improve compatibility, selective-calling facilities, and the s.s.b. radio equipment with synthetiser frequency control with which Piccolo is used. Operational techniques and performance figures are quoted. Other applications of the system are discussed, and possibilities for further development are mentioned.