Does you know what's the difference between EHWIC-4ESG and HWIC-1T ? If you are interesting to know about, you can follow the thing below:

EHWIC-4ESG detail:
Four port 10/100/1000 Base-TX Gigabit Ethernet switch interface card  for Cisco 1900 2900 3900 Routers

The EHWIC-4ESG and 8-port Cisco Gigabit Ethernet Enhanced High-Speed WAN interface cards (EHWICs) can reduce your company's total cost of ownership (TCO) by integrating Gigabit Ethernet (GE) switch ports within Cisco 3900, 2900, and 1900 Series Integrated Services Routers (ISRs).

HWIC-1T detail:
1-Port Serial WAN Interface Card Cisco Router High-Speed WAN Interface card

Serial and asynchronous high-speed WAN interface cards (HWICs) provide highly flexible connections for Cisco1800, 1900, 2800, 2900, 3800, and 3900 Series Integrated Services Routers.