We have a client for whom we’ve installed phones. They have doors with a buzzer button on their old system. Because of construction/wiring issues, it’s best if we reuse the existing door buzzers, which are simply two-wire push buttons. Is there such a device that will generate a SIP call when a contact/swtich is closed? There are many models of door buzzers that will do this, but all we’ve seen would require network cabling to the buzzer, which isn’t feasible.