3Com 56K Command Reference Manual page 182

H-2 A H: V
PPENDIX IEWING
LED
S
This LED Status
TR On
Off
CD On
Off
RS On
Off
CS On
Off
Means your Business Modem
RS232 mode: has detected DTR signal
USB mode: has detected successful USB registration
RS232 mode: has not detected DTR
USB mode: has not detected successful USB registration
Has detected a carrier from a remote device or carrier
detect has been forced on
Has not detected a carrier
Has detected the Ready to Send (RTS) signal from your
computer
Has not detected the RTS signal from your computer
Is sending your computer the Clear to Send (CTS) signal
Is not sending your computer the CTS signal