#29032, "RE: Willet Bruce steam whistle control" In response to In response to 7
To me that indicates one of two possibilities -- either there were two set of apparatus, which would be unusual by what I have seen of other installations, or perhaps this is a more advanced version of the 1909 timer -- maybe one switch to set the duration of minutes or seconds between blasts, and a second to adjust the duration of the blast itself.
There were clearly other variations of these controls as borne out by a Google search of "Willet-Bruce." The search failed to find anything additional on this particular apparatus, but it did get a hit on a site selling old ship fittings which had for sale a Chadburn's whistle control switch with the Willett-Bruce name marked on it. This switch was simply marked "ON" and "OFF" which, to me, means that either the device in this case had only one fixed setting, or this was the momentary manual switch for sounding the whistle(s). At any rate, it does show that different configurations existed, and that until Smith Hyson acquired the sole rights to the Willett-Bruce apparatus in the early 1920's, W. J. Willett-Bruce or Downie & Co. were selling licenses to Chadburn's and probably others, in addition to selling the complete apparatus exclusively through Downie's.