Bidding box for home-played games. Use of bidding boxes has several advantages over oral bidding: it reduces noise in the room, prevents bidding being overheard at neighboring tables, allows easier review of the auction, and reduces the opportunity to pass unauthorized information to one's partner (intentionally or not) by the manner and intonation in which one makes one's bid. A bidding box is typically a plastic box with two slots, each containing a set of bidding cards. One slot contains 35 cards with symbols of bids (5 denominations—clubs (), diamonds (), hearts (), spades (), and notrump (NT)—in seven levels of bidding,
Spectrum auction unjust enrichment of any party, and fostering the rapid deployment of new services, as well as recovering for the public a portion of the value of the spectrum." Despite the apparent success of spectrum auctions, important disadvantages limiting efficiency and revenues are demand reduction and collusive bidding. The information and flexibility in the process of auction can be used to reduce auction prices by tacit collusion. When bidder competition is weak and one bidder holds an apparent advantage to win the auction for specific licenses, other bidders will often choose not to bid for higher prices, hence reducing the final