Hi There

I have used several types of backstage communications and have had pros and cons for each.

The FM transmitters are now old and unobtainable. They were reliable in their day but are now getting quite unreliable and even if they were still available I would avoid using them.

I have used UHF and infact have three of my own with headsets. They are not vox and require you to push a button to talk, which I find great when you are stage managing and dont necessarily want everything heard. The trouble with these is 1) You can get interference from outsiders, although it is rare and you can change channels if this happens. 2) They are only one way communication at a time, which can be a problem when the SM needs to get a message through and some other crew are tieing up the line. However there are some good sides, being that they are cheap, these days you can buy them in packs of two with battery chargers etc. Rechargeable is the way to go, because they do tend to chew through batteries if you are constantly on them, in the case of an SM, I have been known to change batteries after every show, when there are a lot of calls involved. They have a cool function though of being able to scan a restricted number of channels. I have worked some large events where we have used UHF and chosen four channels. One for event admin / management, one for techs, one for security and one for others.. Those who need to listen to all channels, ie Event Managers, can then set their radios to scan the four channels and then they will hear most conversation on all channels. Quite a cool function, although to simple productions, probably not warranted.

Commercial Talkback systems are generally very reliable, two way communication, ie SM can talk over the top of others meaning calls dont get missed or delayed. They are easy to use, usually only a volume knob and a talk/call button. Can't really go wrong, but they are not cheap.

I am currently working with an event company in Sydney who use the motorola two way radios. We have over 50 units on site (Sydney Entertainment Centre) which are used by the stage crew, the event crew, the organisers etc. We use 4 channels and each group sticks to their channel and it all goes well. If you need to talk to someone on the other channel you just switch channels. Motorola has a select number of frequencies to use and programs the handsets accordingly. You can hire the radios from Motorolla and they will program them all up for you and since it is a restricted frequency you dont get outsider interruptions. Each night you just stick them back on charge ready for the next day. Highlyu reliable, and if there are any problems you just give motorola a call and they fix it or swap it right there and then.
But once again probably not ideal, but an option you might consider.

In your situation I dont think you can go past either the UHF system or the commercial talkback system. Just need to way up the costs and see what is best.

Send me an email, greg@donhardt.id.au if you need anymore info.

Cheers

Greg D