In order to use terrestrially transmitted digital TV, DVB-T, for interactive distribution services such as teleshopping, telelearning and telebanking, this service is equipped with a return channel, DVB-RCT. The return channel can use the telephone network or ISDN.
The modulation in the return channel uses Multiple Access OFDM( OFDMA) in the same frequency bands in which the downstream channels transmit the TV signals. Transmission can take place in radio cells up to 65 km in diameter, and at several kilobits per second. The DVB-RCT can also transmit power peaks of several thousand transactions per second. The transmission power for the return channel, which is applied by the user terminal or the set-top box, is 0.5 W.