CANOGA PERKINS 2270 Fiber Optic Modem - Manual (Page 49)

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2270 Fiber Optic Modem
Chapter 4 - Modem Operation
4.1 Modem Operation
Though the actual electronic connection between the data equipment interface and a 2270 Modem
differs from model to model, the electronic conversion from voltage level to optical level is similar in
all applications. Figure 4-1 provides a functional block diagram of a typical 2270 Modem. (For
simplicity, the test circuits are not shown.) The internal clock is shown with a broken line. The
modem is shipped from the factory set to use the external clock. The optional clock may be
selected via front panel switches at the time of installation.
Figure 4-1.
2270 Circuit
Board Diagram
4.2 Fiber Optics
Since light is the transmission medium being used between modems, there are other advantages
over conventional copper wire. In effect, most problems normally associated with large, multicon-
ductor cables are eliminated. These include not only interface distance, but also grounding prob-
lems, Electromagnetic Interference (EMI), Radio Frequency Interference (RFI), and signal radia-
tion. This latter factor is of particular importance where security of the system is important, and for
compliance with FCC compatibility regulations.