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Definition: modem status signals

The following acronyms are used with the status lights on an external analog dial-up modem. For some functions, there is more than one acronym that can be used.

 Acronym  Meaning

 AA       Auto answer mode
 CA       Compression active
 CD       Carrier detect
 CTR      Clear to receive
 CTS      Clear to send
 DTR      Data terminal ready
 EC       Error control active
 HS       High speed (4,800 bps and up)
 LB       Low battery
 MR       Modem ready (data set ready)
 OH       Off hook
 PWR      Power on
 RI       Ringing
 RNG      Ringing
 RTS      Request to send
 RXD      Receiving data
 RD       Receiving data
 SD       Transmitting (sending) data
 TD       Transmitting (sending) data
 TXD      Transmitting (sending) data
 TM       Test mode
 TR       Terminal ready

Modem Status Lights
External modems have the advantage of status lights, which are very helpful when troubleshooting the line.