The conference committee is one of the most important joint committees in het American Congress, appointed to reconcile differences between bills adopted in the two houses of Congress in different forms. Each house is authorized to call for a conference. Usually, only the most important bills are submitted to a conference committee, and minor bills wilt be adopted by concessions of one of the houses. Each house commits his conferees, and can give them instructions on how to vote. These instructions however are not imperative. The number of conferees in each delegation is not necessarily equal, but each delegation votes as a unit and in the way determined by the majority in the delegation. The committee only is allowed to examine the matters in disagreement and cannot add any new provisions to the bills. When an agreement is reached a conference report is written and signed by the majority of the conferees in each delegation, after which it is sent back to the houses for approval. The bill as modified by the conference committee can be adopted or rejected, in which case a second conference can be asked for. No amendments are allowed. The conference committee, sometimes called the «Third House of Congress» not only has become a very powerful institution but also a necessary one. It is responsible for about one third of the legislation including the most important bills. Its necessity is confirmed by its two century-existence, and the fact that it has been copied in other federal states such as the Federal Republic of Germany and Switzerland.