A gateway 11 for using non-IP digital telephone handsets 10 with an IP call controller (“PBX”) 12, 24, 42. The gateway may be implemented to work with any non-IP digital telephone handset and any IP call controller. The call controller may be a public protocol IP Centrex call controller 24 or a proprietary protocol call controller 12, 42. The gateway is programmable so that a single hardware unit can be programmed after it is plugged in to work with any such devices. The programming is accomplished via IP download from a server on the global IP network 23. The gateway may be implemented as a plug in card 40 for an IP call controller 42 that accepts plug in cards. Alternatively, it may be implemented to work with remote IP call controllers 12, 42. In this latter configuration, the gateway may include a router for other IP devices which is designed to give voice quality preference to the telephone handsets over other IP devices.