This appendix explains how to view the twelve LEDs on the front of your Courier 56K Business Modem.
| This LED | Status | Means your Courier 56K Business Modem |
| HS | On | Has made a 4800 bps or faster connection. Once this light is on, it remains on until reset. This can be configured with S69. |
| Off | Has not made a 4800 bps or faster connection since last reset | |
| AA | On | Is ready to accept calls |
| Blinking | Has detected an incoming call | |
| Off | Is not ready to accept calls | |
| CD | On | Has detected a carrier from a remote device or carrier detect has been forced on (using DIP switch 6) |
| Off | Has not detected a carrier | |
| OH | On | Has control of the line |
| Off | Does not have control of the line | |
| RD | Flashing | Is sending data to your computer |
| Off | Is idle | |
| SD | Flashing | Is receiving data from your computer |
| Off | Is idle | |
| DTR | On | Has received a Data Terminal Ready (DTR) signal from your computer, or DTR is forced on (using DIP switch 1) |
| Off | Has not detected DTR | |
| MR | On | Is powered on |
| Flashing | Is retraining with a remote device or is in Test mode | |
| Off | Is powered off | |
| RTS | On | Has detected the Ready to Send (RTS) signal from your computer |
| Off | Has not detected the RTS signal from your computer | |
| CTS | On | Is sending your computer the Clear to Send (CTS) signal |
| Off | Is not sending your computer the CTS signal | |
| SYN | On | Is in synchronous mode |
| Blinking | Has activated Dial Security | |
| Off | Is not in synchronous mode/Dial Security not active | |
| ARQ/FAX | On | Is using V.42 bis error correction |
| Flashing | Is retransmitting data to the remote modem | |
| Blinking | Is in fax mode | |
| Off | Is not using error control, not retransmitting data, and not faxing |