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 (see Fig. 1). Voltages in the range -12V…+12V at the O/I resp. I/O sockets can be processed by the module.

Four LEDs indicate the active in / output (ie. the on that is connected to the out / input at any particular time).

With an additional switch the number of steps can be set to 2, 3 or 4. Moreover the revised module allows to process voltages in the full A-100 voltage range (i.e. -12V…+12V).