Within the premises data communications environment, economies
can often be gained by sharing resources. Such resource sharing
may take a number of different forms. The communication capacity,
that is the actual cable, can be shared by a number of different
data sources or their applications. Communication and peripheral
equipment can also be shared.
One of the most commonly encountered sharing problems is that
of sharing the interface connector on a data device. The RS-232
interface itself is the most widely used. A typical need is
to be able 'to split' this so that several data devices can
be connected to another through the same RS-232 interface.
The Model 31 'Port Miser' is a convenient device that allows
such sharing and effectively expands an RS-232 port by three.
It requires neither AC nor DC power for operation. It can handle
data at a rate of up to 19.2 KBPS from each connected device.
The use of the Model 31 in a typical application is shown in
the illustration above. Here a PC needs to be connected to three
peripherals: a Magnetic Stripe Reader, a Bar Code Scanner and
a Keypad Module. However, the PC has only one RS-232 interface
port that is unused and available. The Model 31 allows the PC
to split the one unused port into three and connect to all three
devices. Of course, which device it addresses at any particular
time is handled by software within the PC.