If galvanic isolation is accomplished by optocouplers, digital signals can be transmitted fast and without interferences in an optical way.
The OI optocoupler boards from BMC Messsysteme GmbH provide 16 digital inputs as well as 16 digital outputs at a Sub-D37 connector electrically isolated from the connected measuring system (--> http://www.bmcm.eu/...).
Customized to a great variety of requirements these have been developed in different versions: the internal version (OI16-PC) is connected to a PC measuring card, the PC/104 type (OI104) is integrated in a PC/104 system.
Especially to mention is the external version OI16 with DIN rail carrier. It has been optimized for connecting the digital I/O interface USB-PIO (--> http://www.usb-pio.de). The digital measurement system used by a large range of customers, which itself has the size and form of a Sub-D connector, can be plugged directly to the OI16 via a Sub-D25 connector. Is there an easier way?
The OI optocoupler boards from BMC Messsysteme GmbH are an example for how standards in measurement technology can be realized in a simple, direct and practical way.