The Phaser device is a kind of hardware based virus protector. The device is plugged into the disk drive port and if you have a second disk drive it's plugged into the back of the Phaser. On the front is a set of LED's which indicates which side of the disk is being accessed, and which disk drive is being used. A further pair of lights show whether the computer is reading or writing the disk. The last light indicates the protection staus of the disk. A switch on the back allows you to protect the disk electronically.
With the Phaser attached and set to protect you can insert unprotected disks, knowing that nothing can infect it. When set correct the Phaser can also be used as a virus killer. The Phaser was bundled with the softeare "Master Killer". Part of this information is from CU Amiga 1991, june issue..