What are those translation devices you see at the UN called?
Solution 1:
Insiders refer to these devices also RF receivers or FM receivers (when working with radio frequency technology) or IR receivers (for infrared). More info can be obtained in The Beginners Guide to Wireless Interpretation Equipment Rental
Solution 2:
If they receive an infrared or radio signal, the devices are infrared or radio receivers with attached headphones. The whole UN process is described here: http://www.slate.com/articles/news_and_politics/explainer/2009/09/lost_in_translation.html