POLY Ehs Cable APP-51 38439-11. Plantronics and Polycom are now Poly. Electronic Hook Switch Cable for remote desk phone call control (answer/end). This cable eliminates the need for a HL10 Handset Lifter. This cable works with Polycom desk phones and may work with additional manufacturers. Replacement Note: The APP-51 EHS cable replaces the APS-50 cable and features compatibility with the Plantronics On-line Indicator accessory.