The c2800nm-adventerprisek9-mz.152-1.T.bin image provides the Advanced Enterprise feature set for Cisco 2800 Series ISRs, supporting advanced routing, security, and VoIP. This 15.2(1)T release improves stability and adds features like transmit flow control, requiring 256MB DRAM and 64MB Flash. For detailed release notes, visit Cisco . Release Notes for Cisco IOS Release 15.2(1)GC
Do not just TFTP this image onto any 2800. Verify your hardware first.