When the Glendale Centre Theatre in California began work on Pajama Game this summer, special effects designer Nick Van Houten wondered how to keep actors safe while the jealous Hines throws knives at a girlfriend he fears is cheating on him. “In a proscenium production, as a fellow deck crew friend of mine tells me, there is an operator scrunched inside the desk who releases the knives on cue [as the actor makes a throwing motion.]” Sounds like a plan — but not for the GCT's theatre-in-the-round, where it would be impossible to conceal an operator.

Van Houton knew he had to find a way to create a consistent effect. If a board operator could control the knives, he would save some money while solving the problem. But could he make this work?


Van Houton turned to Wireless Solutions' Wireless DMX Black-Box System. “The wireless receiver was connected to a DMX relay module from Blue Point Engineering, which in turn was connected to solenoids which deployed the spring-loaded knives from within the desk,” he explains. “Power was supplied from a Xpower Powerpack 400 Plus kept within one of the desk drawers. On the other end of the line, our ETC Express 48/96 provided three cues within the scene, each wirelessly transmitting signal to release one of the three knives in the desk.”

Crews cut permanent holes on the top of the desk through which the knives passed. By placing a new piece of blotter paper on the desk for each performance, the knives appear to pierce the desktop.

Van Houten says he had purchased small lighting effects from Blue Point Engineering for another project. “When I saw the DMX relay unit, it immediately sparked my interest for use in theatre. Similar products cost several hundred dollars, so this seemed like an extremely good deal. We had previously purchased one of the same relay modules for our booth, which we use for triggering our on/off effects — hazer, practical doorbell, practical telephone, practical buzzer, and others — from our lighting console.”

When approached for the knife effect, he knew the relay module would be perfect. But Van Houten says the wireless DMX was the key device. He had looked at similar devices from City Theatrical, Avolites, and Martin, but none were quite right for their needs. “I had seen another system that used Bluetooth technology, but I had heard reviews that the system was not reliable. And then, I stumbled across Sweden-based, Wireless Solutions' system. It appeared too good to be true — small transmitters and receivers, secure frequencies, low price, and no settings to fuss with. I contacted the American Distributor, Sand Network Systems, and they soon sent me a loaner/test system.”

With the help of his sales rep, Hans Lau, who communicated with the vendor, “it worked immediately out of the box.” Installed in the desk, along with the power supply, relay module, and knife release mechanisms, “it worked like a dream.”

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