Complex sentence: A mobile phone jammer is an instrument used to prevent cellular phones from receiving signals from basen practically any location, but are found primarily in places where a phone call would be particularly disruptive because silence is expected.
Split into simpler sentences: A mobile phone jammer is an instrument used to prevent cellular phones from receiving signals from base stations. These devices can be used in practically any location, but are found primarily in places where a phone call would be particularly disruptive because silence is expected.