If everyone has a Hornby Supersound kicking around somewhere, this is a slightly rarer beast.
The AGW PE 109 Sound generator appears to date from the 1960s - it's metal case is shared with a rather nice transistorised controller the same company produced from the time.
On the back, there are inputs for 15V AC (16V works just as well and is more readly available from model railway controllers), an external speaker and something called "Remote"
I'm assuming this last input replicated the operating button on the front face allowing some cleaver jiggery pokery that will fire the sound when a loco passes a Whistle board or similar. Either that or you can mount remote buttons around the layout.
Inside the box is a speaker that provides plenty of volume - there is no control over this.
On the front, a rotary switch, also shared with the controller, selects between a single diesel horn and 4 increasingly shrill steam whistles. There's an Off position too which seems superfluous but someone must have thought it a good idea at the time. The operating button is a pleasing red colour as all such buttons should be.
If I'm honest, the sound isn't very good. More white noise - the unit must have an AC feed presumably to provide the necessary "wobble" to drive this. I tried a 9V battery and only produced a single click sound.
Anyway, sit back, fire up the video below and enjoy the sounds of the (nineteen) sixties.