It includes trigger and reset inputs, four in / outputs, and a common out / input. Each time a pulse is received at the trigger input socket, the common out / input is connected to the next in / output. After the fourth in / output, the next trigger makes it step back to the first again, and so on. A positive pulse at the reset input switches the out / input immediately back to the first in / output.
Voltages in the range -12V...+12V at the O/I resp. I/O sockets can be processed by the module (not only control voltages but also gate, trigger or clock signals provided that they are in the -12V...+12V range).
By means of a toggle switch the number of steps can be limited to 2, 3 or 4.
Four LEDs indicate the active in / output (ie. the on that is connected to the out / input at any particular time).
For more detailed information please look at the English user's manual: A151_man.pdf.