For more than ten years Shure's MX-Series of installed microphone products has offered specifications and performance unrivaled in the Industry. This has included the seldom-mentioned spec of RF (Radio Frequency) rejection. In fact the MX-Series design was so effective it would routinely be specified as either microphone of choice or replacement for original equipment in "difficult" RF environments, where other brands would fail.

Several years ago a new digital phone technology appeared. Known as GSM or Global System for Mobile Communications, this new system grew in popularity and is now the standard for Cellular Phone and BlackBerry communications. Unfortunately, it also redefined intrusive RF interference and even the extremely robust MX-Series was affected.

The characteristic signature of GSM interference in an audio device is an irritating and very disruptive combination of a loud clicking and buzzing sound. The easiest way to intentionally hear it is to hold a GSM cell phone or BlackBerry against a standard landline telephone while holding its handset to you ear and pressing send on the cell phone.

When GSM phones were introduced, they were reported to produce a deafening sound for some hearing aid wearers and to interfere with critical electronic medical devices such as pacemakers. Swedish hospitals banned them, as have many in North America. One Australian newspaper reported that a motorist deployed his airbag with one and, in Paris; they were said to occasionally reset taximeters to zero.

Shure aggressively addressed this problem three years ago with a very successful re-design of the MX Series and the result was their new CommShield Technology. Many models of these new GSM immune mics have been in stock and shipping from SF Marketing for the past year.

The new RF Immune models can be identified by the box label that states "RF Filtering" or RoHS COMPLIANT or by a dot located on the attached or in-line preamp. Field tests have shown the new designs to be totally effective