Wired vs. wireless
There are two ways headsets are powered. One way is by DC, which is batteries (rechargeables save a lot of money – you can spend hundreds of dollars a year on headset batteries - so be sure to include rechargables in your spec's or purchases). The other is by AC, which is plugged into the theatre's hardwired system by way of a cable. Both wireless and wired headsets have their benefits and you should spec some of each.
Wired headsets don't eat up batteries, and are best for people who don't have to walk around. For instance, the light board and sound board operators don't usually have to leave their positions during a show, nor do the followspot operators, because boards and followspots are not portable. (Although, that said, even board operators occasionally have to get up from their post to attend to something that might be happening ten feet away. With a wired headset they would then would have to temporarily 'go off headset' and might miss a cue being called.)
Wireless headsets are best for crew who need to move around, such as a fly system operator. They may have to fly out a drop on Lineset 6 and then rush to fly in a drop at Lineset 20. The fly rail area can be a dangerous place (see The Counterweight System chapter), and although there may be policies that any actor waiting in the wings should stay away from the fly rail, it's not always possible because of space considerations. Imagine what would happen if the crew member on a headset attached to the wall with a 20' wire were to have to move between actors and other crew standing in the wings. The cable would be a big tripping hazard.
Another person who has to move around backstage is a Mic Wrangler. This is the person who is in charge of placing mics on actors who might be sharing them, and is in charge of replacing dead batteries if they occur during a show.
Likewise for the House Manager who has to move around the lobby, in and out of audience members, concession sellers, and the box office. A cable would be very impractical.
WHO GETS WHICH
From our original list of positions, here's who should have what headset capability.
The Stage Manager should have both options; a wired headset in the booth if they are calling the show from the booth and a wireless headset to wear if they are calling the show from backstage.
Light Board Operator
The Light Board operator can make do with a wired headset most of the time, but a wireless headset would be optimal.
Sound Board Operator
The Sound Board operator (located in the house, because you've read this book) can make do with a wired headset most of the time, but a wireless headset would be optimal.
Followspot operators rarely have to move from their positions, because they are usually located in the beams or catwalks or another position away from distractions. So they can have wired headsets. Ideally, though, they should each be able to plug into their own jacks, even if they are standing next to each other. The headset wires should be carefully located and taped down so that there is no tripping hazard.
Flyman/Fly Rail Side of the Stage
Wireless. Tripping hazard. Say no more.
Stage Right or Left – the other side of the stage from the fly rail
Get out your crystal ball and decide if the person standing back stage will be issuing orders from where they stand, or whether they will need to move around for set changes, etc. A wired headset is better than no headset, but a wireless headset would be the best choice for flexibility in a variety of show situations.
Center of House – tech table position
These – at least two jacks are optimal – can be wired. If someone needs to go off headset while at the tech table during a rehearsal, that's ok. It's not likely that anyone would be sitting at a tech table in the house during a show, when leaving a headset could jeopardize the show.