Motorola V186 - Cell Phone - GSM System Planner Manual page 104

• Cable characteristic impedance: Distributed capacitance and inductance slows
edges, reducing noise margin and compromising the 'eye pattern'. Distributed
resistance attenuates the signal level directly.
• Termination: A long cable can act like a transmission line. Terminating the cable
with its characteristic impedance reduces reflections and increases the achievable
data rate.
Although normally required at higher transmission frequencies, it is good practice to
terminate the cable runs with a resistor equal to the characteristic impedance of the cable.
This reduces the reflection of a signal when it reaches the end of the cable. Avoid adding
a termination resistor at other locations as this can overload the driver and reduce the
reliability of the data transfer. The distance can be increased by the use of repeaters.
100
Communications