7 CONTROLLING EIA-232SIGNALINGThis chapter contains information about configuring the EIA-232 1signalling between your computer and modem:n Data Terminal Readyn Data Set Readyn Carrier DetectData TerminalReadyYour computer sends a Data Terminal Ready (DTR) signal to the BusinessModem when it is ready to send and receive data. The &Dn commandtells the modem how to respond to the DTR signal.Example: Sending AT&D1 before connecting with another device,dropping DTR will enter Command Mode.1.The EIA-232 Standard was formerly known as RS-232 (RS stands forRecommended Standard).For your modem to CommandIgnore the state of DTR and act as if DTR is always present. Usethis command with equipment that cannot provide DTR.AT&D0If issued before connecting with another device, enter onlineCommand Mode during a call by dropping DTR. Mostcommunications software packages have a method fortoggling DTR. Refer to your software’s manual for details.AT&D1Respond normally to the DTR signal.The Business Modem will not accept commands until yourcomputer sends a DTR signal. The call will end when the DTRsignal is dropped.To change the DTR recognition time, setS-Register 25. See Appendix A, S-Registers for moreinformation.AT&D2Business Modem hangs up and resets upon loss of DTR signal. AT&D3
