USRobotics V.34 user manual What You Need to Know

COURIER HIGH SPEED MODEMS

NOTE: The term DTE in the following discussion means Data Terminal Equipment, the end-to-end equipment involved in data communications. DTE denotes your terminal or computer and the remote computer.

What You Need to Know

The network's communications management staff can supply information on the following requirements:

•The protocol needed for your calls

•The software support needed to log into the network; for example, a specific communications package or interface board

•The phone number, if you will be calling instead of answering

•Any restrictions about when you can call

The RS-232 Interface

Transmit and Receive synchronous timing pins are required at the RS-232 interface. You'll need either pin 15 or pin 24 for Transmitter timing signals, depending on whether the modem (pin 15) or the DTE (pin 24) generates the signals. You'll also need pin 17, for Receiver timing signals. If you're building your own cable, review the RS-232 Interface, in Appendix B.

Protocol Compatibility

The devices at both ends of the link must use the same protocol. These protocols format data into blocks or frames and add control information.

If the modem is in V.25 bis mode, the link protocol must be HDLC (High-Level Data Link Control), or character-oriented. If the modem is in Online Synchronous mode it may use HDLC, character-oriented, or another protocol determined by the mainframe manufacturer.

F-2 Synchronous Operations