We had the problem of concurrent users locking up a tape drive.We tried a white board, we tried a sign in/out sheet, it got so bad that we held a meeting and the manager decided we would use the ownership of a certain file to show who was allowed to control the tape drive. The same manager broke his own rule immediately after the meeting.My solution was the one that worked. We used a really cheesy Mardi Gras necklace. Who ever had the necklace in their possession was allowed to access the tape drive. We never had a problem after that. If you left the necklace on your desk it was perfectly okay for someone else to steal it. If you wore the cheesy thing around your neck, everyone knew you were using the tape drive.

Sometime low tech is easier, more reliable and best of all, funnier.