ATA5577, commonly referred to as T5577, was formerly a technology developed by Atmel that is owned now by Microchip. ATA5577 (T5577) is a very popular Low Frequency operating at 125kHz. It is compatible with Microchip's T5557/ATA5567 and a replacement for the e5551/T5551 in many common operations.
T5577 has a frequency of 125KHz but its strength comes from the fact it is a re-writable technology so it can flexibly imitate UID/card numbering of other 125KHz formats, making them easy to configure with compatible 125KHz readers. The technology is popular for physical access control to business premises and in hotels or applications in general where the chip number is read for identification purposes.
Universal Smart Cards can support various form factors including PVC Cards, Keyfobs, Tags and Adhesive labels.