Carnets are our prepayment system. Typically, each carnet token covers one 5 MHz bandwidth unit for each use of up to 48 hours and offers a 10 - 30% discount on the standard fee. But note that the new online carnet covers a 10 MHz channel for each use of up to 12hours.
Standard carnet tokens for video links cover 5 MHz of bandwidth for up to 48 hours use. eg. A digital 10 MHz bandwidth link (or low power 2 - 5 GHz analogue) will use 2 tokens, an analogue 20 MHz link will use 4.
On-line carnets cover 10 MHz bandwidth but only for a 12 hour period.