Cisco 1605-R How To Use Manual page 50

Serial Cards
Note
interface cards support synchronous data rates up to 2.048 mbps.
In the Cisco 1720 router, the 1-port and 2-port serial WAN interface cards support both
asynchronous and synchronous data rates up to 2.048 mbps.
In Cisco 1600 series routers, the 1-port serial WAN interface cards support asynchronous
data rates up to 115.2 kbps, and synchronous data rates up to 2.048 mbps.
Each serial card has one LED, labeled CONN for each port, which lights when the serial
port is connected. When the port is in DTE mode, the CONN LED indicates that Data Send
Ready (DSR), Data Carrier Detect (DCD), and Clear To Send (CTS) have been detected.
When the port is in DCE mode, it indicates that Data Terminal Ready (DTR) and Ready To
Send (RTS) have been detected.
Figure 3-1
3-2 Cisco WAN Interface Cards Hardware Installation Guide
In Cisco 3600 and Cisco 2600 series routers, the 1-port and 2-port serial WAN
1-Port Serial WAN Interface Card—Front Panel
Serial port CONN LED
CONN SERIAL