You require a PC and a Modem as the Hardware. Any communication software can be used for connecting to Inet. e.g. Hyper term which is already available with Windows can be used.

You require a PC with any communications software. e.g. Hyper term which is already available with Windows can be used. The modem shall be provided by the BSNL.

You require at least a PC, an X.25 Router or an X.25 PAD. You should be able to configure the PAD/Router. The modem MAY be provided by the BSNL in some cases (depends on local availability). The software required is normally available with the vendor from whom the PAD/Router is purchased.