Analogue Board
The analogue board provides the interface circuitry between the monitored and control telephone lines and the microprocessor. The board contains the following devices ;
U1 = OP490 Quad Op-Amp U2 = Mitel MT8870CE DTMF Decoder U3 = Motorola MC145442 V.21 300Baud Modem U4 = LM358N U5 = Phillips 74HC157PThe board also contain a 25-way female D-type connector that provides the electrical interface to the monitored/control lines. Alternatively, it provides an RS-232 interface thereby enabling the direct connection of a PC running the Dialog software.
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