Here is what you need to know about how to transfer a call or to make a call programmatically using RingCentral Call Control API.
1. To transfer a call, you need a phone number to transfer the call. That number can be the number assigned to a physical device as you ask for.
2. To dial a number from a physical phone, you need to have the device id then use the call-out API to dial.
To check the phone number of a physical phone and to detect the device id of a physical phone, you can read the user devices to pick the phone number or the device id required by the APIs mentioned above.
Further readings
https://medium.com/ringcentral-developers/ringcentral-telephony-session-events-notifications-98b3f8d29745
https://developers.ringcentral.com/guide/voice/call-control
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