The banners are downloaded from the exchange. A monitor on the exchange determines, from referral information supplied by web browsers, how many times a member web site has displayed the banner advertisements of other members, and credits that member with a number of displays of its banner on some other member's web site. Link exchanges usually operate on a 2:1 ratio, such that for every two times a member shows a second member's banner advertisement, that second member displays the first member's banner advertisement.