Because of the noise and vibration, early experiments had shown that radios were impractical, therefore lamps, flags, semaphore, coloured discs, and the carrier pigeons were part of the standard equipment of the various marks.
På brung af støjen og vibrationerne havde tidlige eksperimenter vist, at radioer ikke kunne bruges, og derfor var lamper, flag, semaforer, farvede plader og brevduer del af standardudstyret i de forskellige modeller.