Editing Broadband over power lines (section)

==Failure scenarios==
There are many ways in which the communication signal may have error introduced into it. Interference, cross chatter, some active devices, and some passive devices all introduce noise or attenuation into the signal. When error becomes significant the devices controlled by the unreliable signal may fail, become inoperative, or operate in an undesirable fashion.

# '''Interference:''' Interference from nearby systems can cause signal degradation as the modem may not be able to determine a specific frequency among many signals in the same bandwidth.
# '''Signal degradation by active devices''': Devices such as relays, transistors, and rectifiers create noise in their respective systems, increasing the likelihood of signal degradation. [[Arc-fault circuit interrupter]] (AFCI) devices, required by some recent electrical codes for living spaces, may also attenuate the signals.<ref>A Work in Progress: Belkin Gigabit Powerline HD available at http://www.smallnetbuilder.com/lanwan/lanwan-reviews/30888-a-work-in-progress-belkin-gigabit-powerline-hd-starter-kit-reviewed?start=4</ref>
# '''Signal attenuation by passive devices''': Transformers and DC–DC converters attenuate the input frequency signal almost completely. "Bypass" devices become necessary for the signal to be passed on to the receiving node. A bypass device may consist of three stages, a filter in series with a protection stage and coupler, placed in parallel with the passive device.