Check the listing for details. Poly CS540 Wireless DECT Headset (Plantronics) – Single Ear (Mono). Color: Black, Condition: Open box. Listed at 159.00 USD. EXTENDED RANGE AND TALK TIME: The adaptive power system optimizes for range and talk time by automatically downshifting to low power when the headset is close to the base. SOUNDGUARD TECHNOLOGY: SoundGuard acoustic limiting technology protects against Acoustic Shock by limiting sounds to below 118dBA ensuring listening comfort and protection against audio spikes. SUPERIOR AUDIO QUALITY: Your choice of narrow or wideband professional grade audio quality -- choose narrowband to extend talk time or wideband mode to enable clearer conversations. MAXIMUM PROTECTION: The CS540 headset includes DECTTM technology that provides better audio quality and eliminates interference from Wi-Fi networks while calls stay safe and secure.