| 摘要 |
PURPOSE: A data transmission system for data communication in a dedicated analog line is provided to achieve data communication in a dedicated analog line by supporting an FXS(Foreign eXchange Station) interface. CONSTITUTION: A data transmission system is comprised of a main processor unit(20), a modem part(21), a ROM part(22), a memory part(23), an impedance matching part(24), a hybrid 2-4 wire conversion part(25), an internal ring generation part(26), and an FXS signaling part(27). The modem part(21) modulates and transmits the serial or parallel data inputted from the main processor unit(20) in accordance with a voice frequency band of 4KHz according to a preset modulation mode. Also the modem part(21) demodulates the data received through a leased line and transfers the demodulated data to the main processor unit(20). The ROM part(22) stores an initial code necessary for the modem part(21) and a control program to control the operations of the modem part(21). The memory part(23) stores data necessary for the present operation of the modem among the data stored in the ROM part(12). The impedance matching part(24) provides impedance matching to make the impedance of the data transmission system equal to the impedance of a dedicated analog line. The hybrid 2-4 wire conversion part(25) converts a 2-wire system into a 4-wire system in transmitting and receiving signals. The internal ring generation part(26) simulates a ring signal internally. The FXS signaling part(27) provides an FXS interface to the data transmission system.
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