The plantronics 86009 01 telephone interface cable is compatible with both the cs500 as well as the savi office range the 4 pin module plugs into the handset or headset port of your desk phone the rj 45 end plugs into the back end of the wirless charging base the telephone handset plugs into the middle of the cord conductor copper product dimensions 197 x 14 x 06 cm 32 kg compatible with the following plantronics models savi w710 savi