Dialpad supports a number of SIP-based IP desk phones, whether purchased directly from Dialpad or bought from another provider. Included here are just a few examples.
VVX x50 Series - 250, 350, 450
Firmware - 188.8.131.5248
VVX Series:101, 201, 300/310, 301/311, 400/410, 401/411, 500, 501, 600, 601, 1500
Firmware 184.108.40.2060+ or 220.127.116.1132
*Although you may be able to connect other SIP phones to your Dialpad account, none of the phone features beyond dial tone should be expected to work. Additionally, you should be aware that no phone beyond those listed above has been tested with Dialpad and therefore Dialpad cannot guarantee that they will continue to work in the future.