Yes. The Plantronics CS50 is compatible various Cisco IP phones including 7942G, 7945G, 7962G, 7965G, 7975G. If you want to answer remotely in order to hangup/pickup from the headset while roaming the office you'll also want to use the Plantronics APC-41 EHS adapter for Cisco. The Plantronics APC-41 (replaces the APC-4). Plantronics no longer manufacturers the CS55 nor CS50. See replacement models below.
For instructions on using the APC-41 with your Cisco phone download the Hookswitch Guide PDF. The Plantronics APC-41 is compatible with the following Cisco phones: 7942G, 7945G, 7962G, 7965G, 7975G. Other Cisco phones require the HL-10 remote lifter to allow the headset to pickup/hang-up calls. For complete details on Remote Answering with a Plantronics download the Hookswitch Guide.
If you have questions about your Cisco phone compatibility and which accessory is required for your Cisco phone feel free to start a chat session or call us at 703-766-6363. Global Teck Worldwide provides a ProSetup Service that walks you through the complete installation and troubleshoot of any headset on our website.