Steven and Struther
of 32 Elliot Street, Glasgow
1886 Description and drawings of Steven and Struther's steam siren. 'The syren and the slotted disc through which the steam is admitted are driven by the same shaft, the former by means of a worm and wormwheel which gives motion to an eccentric working a pawl at the upper end of the eccentric rod. This pawl actuates a ratchet wheel fast on the same spindle that carries the slotted disc to the back of which steam is admitted by the supply pipe .... ; the second slotted disc, with which the first one is in contact, is driven by a pulley and strap from the end of the engine shaft. By this arrangement the duration and character of the signals, as well as the intervals of silence, can be regulated at pleasure, while the mouth-piece is capable of being adjusted horizontally. The manufacturers make a speciality of this instrument in combination with a steam whistle for use at sea, the two together affording a means of efficient and varied signalling with the Morse code, or on any other system.'[1]