Some telephones, depending on the brand and model, have the intercom function, which allows to begin communication by sending the signal. When the signal comes, the telephone set rings a signal different from the standard ring tone call. After that the telephone temporarily switches off from the telephone line and works as an intercom.
Dialtel is an International Wholesale and Retail Carrier. We mostly focus on destinations in Africa, Middle East and Asia. Attached I am sending our Push list. Please check it and let me know whether you can use any of the routes.