There are many different brands of these intercoms, but I hate them all.
Selling tickets through glass places a barrier between the ticket seller and the customer. This barrier can cause misunderstandings and rudeness. We turned our box office 90 degrees and we sell inside now. If I were building a new theatre I would have the box offices inside with about a 40" counter between the customer and the cashier. This would lessen reach across problems.
Old theatres used to have the box office outside on the sidewalk. This allowed them to line up people outside. For security there was a window. Now we design lobbies with sufficient space to hold many people inside so why would you sell tickets outside?
Your friendlier banks don't use glass or cages for their tellers anymore unless they are in a high crime area.
The best security is to have the money disappear from the box office early and often. Make drops in a drop safe.
But if you insist on a talk through glass communicator, look for Telex.
http://www.telex.com/
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