The Cisco 1600 series routers are the proven choice for flexible Internet/intranet access for small branch offices and small businesses.  In addition to one fixed WAN port and one Ethernet port, the 1600 series routers support one WAN interface card which allows users to add or change WAN ports as needed. 

WAN options include ISDN, leased lines, Frame Relay, Switched 56, Switched Multimegabit Data Source (SMDS) and X.25.                                                                                              

Models:

1601 - has one serial port with synchronous performance up to T1/E1 speeds for Frame Relay, Leased Line, Switched 56, SMDS and X.25 WAN services or async performance up to 115.2 kbps.

1602 - has a 56-kbps serial port (Frame Relay, Leased Line, Swithced 56, SMDS and X.25) plus a low cost integrated DSU/CSU interface.

1603 - has ISDN (BRI) and ISDN Leased Line capability.

1604 - same as 1603, but adds NT1 capability

1605-R - has TWO Ethernet ports to isolate an internal secure LAN from perimeter LAN plus a single flexible WAN port (accepts and WAN card)