This excerpt taken from the SLTC 10-K filed Oct 3, 2007.
Allowance for Doubtful Accounts
We evaluate the collectability of our accounts receivable based on a combination of factors. When we believe a collectability issue exists with respect to a specific receivable, we record an allowance to reduce that receivable to the amount that we believe to be collectible. In making the evaluations, we will consider the collection history with the customer, its credit rating, communications with the customer as to reasons for the delay in payment, disputes or claims filed by the customer, warranty claims, non-responsiveness of customers to collection calls, feedback from the responsible sales contact. In addition, we will also consider general economic conditions, the age of the receivable and the quality of the collection efforts.