cedd

It mentions adjustable mic gain in the first post. I was very pleased to see it there as I've had just the issue you describe, specifically between the new plastic ASL packs and Metro/Stonewood (and now Granite!) systems. Vibration motors are surprisingly cheap. Como Drills make them and I've used a couple in a project recently. Worked really well. They'd probably run off of the lamp circuit happily enough as they require very little current, though they also only run on something like 3V, so a bit of tweaking required.

On a similar line to dbuckley's suggestion, would it be possible to add a couple of terminals (could be just solder pads) in the audio path after the mic pre amp and also in the output stage before the headphone amp? It'd mean you could use the same pcb to make a master station with line in and out. It'd also give options in the future for building 2 channel master stations and beltpacks just by strapping a pair of pcb's together with suitable buffering. Not something I'm suggesting you'd design, but it'd give a little assistance to the DIY'er who was using them as a starting point. 2 sockets in parallel is a nice touch. I hate soldering tinsel wire (he says looking at the box of 16 radio mic headsets all needing reterminating) and whilst I've grown pretty good at them over the years and I think a 4 pin XLR is infinitely better, I take the point that it's probably more hassle than it's worth changing the plug on a cheapo headset, especially as the factory fitted moulded plug is probably far better than I'll ever manage with my soldering iron. As an aside, and whilst I understand this is an open source project and really appreciate you're making all of this available for free, I really wouldn't mind a few quid heading in to your pockets for the work you've done! Maybe if that's difficult you could set up a donate function so happy users can send a bit of a thank you? Might only be beer money from some, but I'd consider it a very worthwhile thing to do.

Does the design mean there's got to be a seperate connector if it's an electret mic? Or are you just providing two for ease of use? My preference is as above, to chop off the 3.5mm jack and replace with 4 pin XLR, but I can see that two connectors might be of use if other users aren't as good at soldering.

That's a really nice neat sized enclosure too! Nice to see it's not the size of a brick like some I've seen (including my first stab at homemade comms!). Did you get it working with cheap pc headsets in the end? There are some quite nice gaming ones for around the £30 mark that'll be nice disposable ones for schools work. Do I guess the power supply is just a supply with a terminating resistor? I'll certainly be buying some!

I still marvel at humanity's ability to take good video footage on a phone while something disastrous is happening! Got to be honest, I think getting my phone out to snap some video would be the last thing on my mind, either as a punter or as crew!

I was thinking of something similair, although it involved placing an in-ear headphone driver inside the earshell of the comms headset. Otherwise, I think you're wise to make your mix post-beltpack, in line with the headset. You could make an adaptor to lift power from the comms system line (XLR male to female short lead, with a pair of wires connected to the DC supply pins to "break out" the DC supply) and then use a summing amplifier and headphone amp to mix your two signals together.

Know you're a new poster, but it's worthwhile searching the BR before starting a new post. A quick search for "safety curtain" in the search box came up with this; http://www.blue-room.org.uk/wiki/Safety_Curtain Which should answer all your questions. There was also a very interesting thread on this regarding watering systems, winch in and out times and all sorts of other info, but I'll let you find that one. Not a telling off, just a suggestion for next time.