BDSU: BSNL, Calcutta Telephones will install one small unit BDSU at customer premises. This will be connected to the telephone line coming from the IAN equipement installed at the telephone exchange premises. Both telephone as well as PC (Ethernet Port) will be connected to the
BDSU. BDSU requires 230V A.C to operate. It combines voice and internet data packets on a single twisted-pair.wire at the subscriber premises. IAN: IAN separates the telephone signal and the internet traffic at the telephone exchange premises. While telephone signal is sent to the telephone exchange. Internet traffic will be sent to the National Internet Backbone of BSNL, bypassing the telephone exchange. | 
