Owners of other interfaces than Service USB core can neglect the following chapter.

Service USB core is used as the base for proprietary development. It is an open frame printed circuit with four digital inputs and four digital outputs. The I/O ports work with 5V logic and have no protection against overvoltage. The large assortment of additional software makes it possible to control the interface of nearly every program.
System requirements
A Macintosh with USB and OSX 10.3 to 10.5 is required to operate Service USB plus. Up to 100 Service USBs can be run on a Macintosh.
Scope of delivery
Furthermore you will find Quicktime-Films about fischertechnik®-models, and a detailed instruction manual.
Hardware description
This is Service USB core top view including all connectors and control lamps:

Service USB core top view
Service USB core has the following connections and interfaces:
Dimensions and connectors

Service USB core top view dimensions and pinout
5V - Auxiliary output voltage. This is 5V from USB, fused with 100mA self resetting fuse.
O3-O0 - Digital outputs bit 3 to bit 0 with 5V logic level. Each output can draw a current of 6mA maximum.
I3-I0 - Digital inputs bit 3 to bit 0. The input current is less than 1µA. Unconnected inputs can switch by receiving static voltage through the air or by a wet finger. It is suggested to connect unused inputs to 0V (GND)
0V - All voltage instructions refer to this connection. It is the 0 volt reference point for all inputs and outputs. It is also known as ground (GND).
Warning: Under no circumstances a voltage more than 5V or a negative voltage is to be connected on any I/O.
Connection with ribbon cable
Commercially available flat ribbon cables with 2.54mm (0.1") female header can be used to connect Service and other printed circuit boards.

Service USB core with flat ribbon cable connection
Because the Service USB I/O lines are logic lines with 5V, the cable should be as short as possible to minimise external parasitic induction. The cable should be not longer than 20cm.
USB-connector
This connector complies to USB full speed with data transfer rate of 12Mb/s. The maximal power consumption is 100mA. The 5V from USB is the power supply for the Service USB core as well as the auxiliary voltage at the multi pin connector, which is protected with a resettable fuse.
The light emitting diodes
In each case four red LEDs indicate the state of the inputs and the outputs. Because of the high resistance of digital inputs the inputs can switch to a random state if they are not connected. In this case the input LEDs may have a random state or are flickering.
The green 5V LED shows that the Macintosh driver has been connected, that there is no shortage on the auxiliary voltage and that the interface is working properly. This LED must always be on during use.
Technical information
Schematic diagrams

Block diagram of Service USB core

Circuit diagram of Service USB core