A separate element, labeled row H in the patent schematic, activated an indicator lamp when the transmitter and receiver were properly synchronized on a channel the receiver could decode. This was the confirmation signal.
The synchronization mechanism was explicit and specific. Both the ship’s transmitter and the torpedo’s receiver would carry identical paper strips driven by spring clock motors that had been calibrated to run at the same constant speed. At the moment of firing — when the torpedo was released and the connection between torpedo and ship was broken — both mechanisms would begin their strips simultaneously, triggered by the break in a solenoid circuit. From that moment forward, both strips advanced at the same rate, both systems hopped to the same frequencies at the same instants, and neither needed to know what the other was doing.
The torpedo steering was handled by two audio tones. A hundred-cycle tone commanded a left turn; a five-hundred-cycle tone commanded a right turn. Tuned filters at the receiver separated these tones and directed them to the appropriate actuators. The steering mechanism used a solenoid pawl and ratchet to move the rudder one increment per command, with a brake band holding the rudder in position between commands. Crucially, the rudder moved one increment regardless of how long the operator held down the key — keeping each transmission as brief as possible reduced the opportunity for detection.
The patent acknowledged, in its own language, that none of this was entirely without precedent. Remote torpedo control by radio was described as “old.” Radio jamming was identified as a known problem. What was new was the specific proposal to use synchronized frequency hopping controlled by identical paper strips to defeat jamming. That combination — the synchronized hop, the mechanical synchronizer, the player-piano inspiration — was what Lamarr and Antheil were claiming.