[PSUBS-MAILIST] Helle Communication equipment

[Brian Hughes via Personal_Submersibles]

Someone on eBay keeps trying to sell Helle equipment of various types. Most are for hard wiring, but several show up without microphone or transducer,, but clearly designed for thu water com. Just because I'm curious I went looking about for information, but no web search seems to find any. Would be interesting to know the power and frequency. Given the vintage, I'd bet a cold beer it's in the 27 kHz range.

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