IP phones are the desk end of a modern phone system: standard desk sets for offices, expanded models with line keys and displays for reception and dispatch, and conference phones for shared rooms. They connect over the network rather than dedicated phone wiring, which is why the phone purchase is really a phone-system purchase.
Compatibility with the calling platform comes first - phones are provisioned and managed by the system they register to, and a handset the platform does not support never becomes fully functional. Then plan power: most IP phones expect power over Ethernet, so the switch budget in each closet is part of the rollout math. Match models to roles rather than issuing one phone everywhere; reception, conference rooms, and ordinary desks make different demands on buttons and displays. COLAMCO quotes IP phone fleets matched to the calling platform for business, government, and education deployments, alongside the switching that powers them.