My first 10BASE5 network segment

though Yes, the whole reflection thing could get into a bit of a complex discussion involving transmission line theory, but I am an electrical engineer, so here goes: Yes, you need proper termination at either end, or else you get the wrong voltages on the line and cause 'collisions' (well, detect collisions anyway, though there aren't really any until the first reflection comes back from the cable end). And yes, you're supposed to put the nodes 2.5m apart. With only a two node network, and with a really short coax (<1m in my case here), the problem this solves is practically nonexistant. In theory, a properly terminated cable should have virtually no reflections at either end of the cable. In reality, imperfections in the cable, tolerances in your terminators, etc. can cause a small bit of reflection, but it should be mostly negligible. At each node, however, the transceiver places a small load on the coax, and some (small) amount of reflection will occur here. The reason you want the 2.5m spacing is so that you stop any nodes from being a perfect wavelength apart (23.4m minimum) and having their reflections build on each other enough to cause a problem with the signal levels and corrupt data (and trigger a collision). Also, the wavelength of ethernet signalling is 23.4m. This is a full wavelength, not a half as pete said. Ethernet is 10Mbit/second (more accurately, also 10Mbaud), which means normally that the maximum frequency of the raw data signal would actually be 5MHz, but since ethernet uses manchester encoding, there are sequences of bits which can produce a 10MHz signal, as well as sequences of bits which can produce a 5MHz signal. The minimum propagation speed of 802.3 compliant 10BASE5 coax is (IIRC) .78C (C being the speed of light, 3E8 m/s), so taking .78C/10MHz = 23.4m Regards, Joe Zatarski