Revenue Recognition We derive revenues from the following primary sources - equipment (tool or system) sales, spare part sales and service and maintenance contracts. In accordance with the authoritative guidance on revenue recognition, we recognize revenue on equipment sales as follows: 1) for equipment sales of existing products with new specifications and for sales of new products, revenue is recognized upon customer acceptance; 2) for equipment sales to existing customers with previously demonstrated equipment acceptance, or equipment sales to new customers purchasing equipment with established reliability, we recognize revenue on a multiple element approach in which revenue is recognized upon the delivery of the separate elements to the customer. The revenue we recognize on a delivered element is limited to the amount that is not contingent upon the delivery of additional items such as installation and customer acceptance, and upon transfer of title. For equipment sales we generally recognize revenue for 90 percent of the total invoice amount as revenue upon shipment while 100 percent of the equipment's cost is recognized upon shipment. The remaining portion, generally 10 percent of the total invoice amount, is contingent upon customer acceptance and is recognized once installation services are completed and final customer acceptance of the equipment is received. The revenue relating to the undelivered elements is deferred using the relative selling price method, which allocates revenue to each element using the estimated selling prices for the deliverables when vendor-specific objective evidence or third-party evidence is not available. We have determined that the fair value of installation services is substantially less than the 10 percent of the total invoice amount typically assigned to the installation element in our customer agreements. As such, since the amount collectible upon successful installation and customer acceptance exceeds the fair value of the installation services, we defer the amount colle