This cable allows you to easily connect any Plantronics H-series headset or Soundpro SWP headset to most  headset  ready telephones.  It provides microphone amplification to boost transmit level.

Polaris has developed its own version of the Plantronics A10-16 cable which functions in exactly the same way but provides better value.  Please  see related product:  Polaris Amplifier Cord for Plantronics Headsets (SPA908).