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Inspite of the
advancement in the field of telegraphy from the early days of morse
sounders, there are still places in rural sectors which use morse
sounders and transmitters. To provide a nation wide communication
network between these, a terminal, connectable to a concentrator
or existing single wire return circuit was conceived. This terminal
was called Electronic Key Board. But this generated DC signals,
which lead to transmission errors over the telephone network. Hence
the need of converting the DC signals at 300 bps to analog (VF)
signals became necessary. This is achieved by an EKB Modem connected
to an EKB unit. An EKB Modem receives Digital Data signals from
the EKB unit. These signals are then modulated to appropriate levels
and transmitted over P & T lines. The signals received are demodulated
i.e., converted to digital signals and fed to the EKB unit.
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