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Amazon.com: Plantronics - Electronic Hook Switch Cable APP-51 (Poly) - Remote Desk Phone Call Control - Works with Poly Desk Phones : Electronics
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![Converter Adapter | Converts RJ-9 to 2.5mm for phones that have a 2.5mm jack., (2200-11095-002) | Use with APP-50, APP-51 EHS for Polycom, Connecting telephone devices to 2.5mm headset mini jack Converter Adapter | Converts RJ-9 to 2.5mm for phones that have a 2.5mm jack., (2200-11095-002) | Use with APP-50, APP-51 EHS for Polycom, Connecting telephone devices to 2.5mm headset mini jack](https://cdn11.bigcommerce.com/s-dc251/images/stencil/1280x1280/products/811/3061/RJ9_2.5mm_adapter__41590.1504821415.jpg?c=2)