28 Jul
2006
28 Jul
'06
3:09 p.m.
Hi all,
What is the resistance of a 10Base-2 terminating resistor?
Officially 50 Ohms, but that's not a prefered value. 51 Ohms is, and
works fine. I am pretty sure 47 Ohms would be OK too.
Note that the resistors serve 2 purposes -- they terminate the cable (to
remove reflections) and that act as a load for the transmitters, which
are actually current sources. The fact that 2 transmitters transmitting
at the same time will produce double the voltage on the cable is used to
detect colisions, so the resistor value has to be somewhat near right.
Don't fall into the trap of 'Oh, it's a short cable, reflections aren't
a problem, I can use anything'. The collision dections stuff will moan at
you :-)
-tony