Photovolt's American-made Model 577-A, 577-AS and 577 are designed to simplify the determination of appearance characteristics. This rugged portable instrument is easy to operate, sets up in just minutes and provides you with unparalleled flexibility. Now available with serial data port option. The 577-A and 577-AS is the latest verion of the 577. The 577 will be continued to be offered to those users who must use the 577 according to their protocol. Compared to the 577 the 577-A (and 577-AS) is identical , but has automatic gain control, increase electronic stability, CE-compliance, and external power supply.