'''Caution''' - The '''clock source''' can be jumpered to 2MHz (default), or to 1MHz. Moreover, the '''handshaking''' signals (CTS/RTS, DTR/DSR) can be disabled via jumpers. There is no good reason for using the 1MHz setting, nor for disabling handshaking at hardware level - these features are only "good" for provoking compatibility problems with software that expects the jumpers to be set to this or that position.
For the more bizarre part, the handshaking signals are '''disabled''' by default. And, these pre-defined settings are implemented as '''hardwired''' connections on the '''component''' side of the PCB; meaning that one cannot cut these connections once when the components (jumpers) are installed on the PCB. About 15 months later, in the [[Schneiderware Notes|Schneiderware Nachlese]]issue 11-1987, the author did admit that they shipped fully assembled PCBs without cutting these "hidden" connections underneath of the jumpers.
Aside from that, both the PCB and the original schematic haven't been too clear about which pins on the 4-pin jumpers should be connected together (and which of the predefined horizontal & vertical connections should be disconnected). Without good reverse-engineering skills it's been rather frustating (if not impossible) to find the correct jumper settings.