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COMSPHERE 3900 Series Modems
1-2 September 1998 3910-A2-GN32-40
Multipoint Applications
In multipoint applications, leased-line circuits are used for time sharing the same front-end
processor (FEP) port with multiple remote locations. The FEP (via the control modem) regulates
traffic on the line by continuously polling the tributary DTE(s) in a predefined sequence. Only one
tributary can communicate with the control modem at a given time. Modems configured for Trellis
Multipoint (TMp) cannot be used in a point-to-point, constant carrier application. (Refer to Leased
Line in Chapter 5, DCP Configuration, for configuration options.)
Leased Backup Applications
In leased backup applications, a 2-wire leased line is used as the backup facility instead of the
normal 2-wire dial line. Plug the leased line into the jack labeled DIAL on the rear panel of the
modem (see Figure 2-1 in Chapter 2), and enable the Dual_Leased_Ln configuration option. (Refer
to Leased Line in Chapter 5, DCP Configuration, for configuration options.) Except for dialing,
ring indication, and call progression functions, you control the backup function as if it were a
normal dial backup.
COMSPHERE 391x Series Models
The 391x Series family is available in two models: the Model 3910, a 4-wire/2-wire standalone
modem, and the Model 3911, a carrier-mounted version of the standalone unit. Both models offer a
variety of modulation schemes and network enhancements while still providing reliable,
high-speed data transmission using the latest in modem technology.