10-code History

[stone35]

I have been wondering why we use 10-codes. Specifically, why the number 10? If anyone knows let me, us, know.

Thanks in advance,
Stone35

[Vinny Del Giudice]

I don't have an answer but I thought you'd find it interesting that the early wireless telegraph systems used by ships at sea employed Q-signals. For example, QTH means What is your location? QRZ means please repeat message. What's more I think at least a few of the current FDNY 10-signals are based on the old fire alarm telegraph signals. For example, 10-75 for a full first alarm assignment is similar to the old telegraph signal 7-5, at least based on my reading of the FDNY signals. Regards. Vinny.