A callback, in this sense is a method of making low-cost international calls via a third country, usually the United States, where call charges are considerably lower. One variation of this technology was developed by IDT Corporation in 1991. IDT Corp used a hardware solution that was never widely accepted and ultimately failed and was surpassed by a software solution concurrently developed by Jorge Blanco at MCI Telecommunications for The United Nations Development Programme and their staff Wolfgang Scholtes and Kumar Navaratnum.