Plantronics CS540 features the latest in super-lightweight headset design, a slimmer base, expanded range up to 350 feet and 7 hours of continuous talk time. Product includes over-the-head wearing style and three different earloops for over the ear style wearing, for versatile wearing styles. Universal compatibility -- CS540 works with just about any single-or multi-line corded office desk phone. Noise canceling microphone means your callers will hear less of the chatter around you. DECT technology and advanced wideband audio using CAT-iq technology which mean world class security and audio clarity.