ZyXEL Omni 288S User Guide - Page 46

Chapter 6 - Leased Line Operation Chapter 6 - Leased Line Operation A leased line is a permanent telephone line connection between two fixed points. It can be dedicated copper wires or a leased telephone circuit from the telephone company. 4-wire leased lines use one pair of wires to transmit data and a second pair to receive. 2-wire leased lines transmit and receive on the same pair of wires. The Omni 288S supports only 2-wire leased lines. Connecting to a 2-Wire Leased Line The Omni 288S is equipped with a phone jack for dial-up line connections. Connections can also be made to a 2-wire leased line using the same jack. Line Type Setting AT-Command Description AT&L1 The modem is connected to a 2-wire leased line; the line plug should be plugged into the jack assigned LEASED LINE on the rear panel. For the normal dial-up line only models, only 2-wire leased lines can be used and the same phone jack is used for both dial-up and leased-line connections. The dial backup feature is not available in this case. Power Level Setting The Omni 288S's leased-line mode transmission power level can be adjusted from 0 dBm to -27 dBm in 1 dBm increments. If a dial-up model is used for 2wire leased-line connection, the transmission power is limited to -3 dBm. AT-Command AT*P0 AT*P15 Description The default is -9 dBm. The adjustable range is from 0 to -15 dBm, effective in leasedline operation only. If bit 3 of S35 is set, this range will change to -12 to -27 dBm. Leased Line Handshaking In a typical dial-up connection, the originating modem dials the number and waits for the answering modem's carrier signal. The answering modem can be commanded to either answer the call immediately, or after a specified number of rings. In a leased-line connection, the communication circuit between two modems is always present. Dialing and waiting for rings does not occur in this situation. If these two modems want to establish a data link, one must be designated as the 6-1