The Model 268 Opto Isolation Module provides a communications link that
has no electrical connections from one port to the other. Isolation is
an important consideration if a system uses different power sources, has
noisy signals or must operate at different ground potentials.
In a data logging or acquisition system the Model 268 protects against
ground loops between the system controller and monitoring devices. These
ground loops create offset voltages which result in reducing the
system's noise immunity. A non-isolated path allows RF noise and voltage
spikes to appear on the controllers data lines. When this happens the
likelihood of data errors and system faults increase.
The 268 insures against these problems while providing full duplex,
optically isolated signal paths for data, TD and RD, and a control
signal pair selected by internal jumpers (CTS, RTS, DCD, or DTR). In
addition to opto isolation, the Model 268 incorporates micro power DC to
DC converters that generate the necessary operating voltages. There are
two sets of these circuits, one for each port. The Model 268 will
operate even if only TD and RD are connected. The DCE port is
implemented with a DB25 male connector while the DTE port uses a female
DB25 connector. The case is fabricated from aluminum and is not
connected to either port.