commercial door chime/alert

[ultramegabob]

what do you use for a door alert in a commercial building? (magnetic switch on door jamb) residential doorbells will not hold up because people prop doors open and the chime overheats/springs come apart, I have been using plug in transformer with buzzers or dual tone noise makers from RadioShack. I was just wondering what some other options were.

 

[LarryFine]

The "pro" door chimes us a switch that only makes momentary contact upon opening, and no contact upon closing. This has come up before, and others have posted manufacturers and other info.

Stand by.