Cisco SPA500S is a great choice for users who require additional line support, such as receptionists. The Cisco SPA500S easily attaches to the following models of Cisco phones: SPA501G, SPA502G, SPA504G, SPA508G, SPA509G, SPA512G, SPA514G, or SPA525G IP phones via the onboard AUX port. You can connect up to (2) Cisco SPA500S modules, adding an additional 64 lines.
Add up to 64 additional lines to your Cisco Small Business Pro IP Telephone with the Cisco SPA500S 32-Button attendant console module. Each Cisco SPA500S supports 32 lines and you can daisy-chain up to (2) SPA500S to any of the Cisco Small Business Pro line IP Phones.