View source for Bridge tap

{{Refimprove|date=September 2007}}

'''Bridged tap''' or '''bridge tap''' is a long-used method of cabling for telephone lines. One cable pair (of wires) will "appear" in several different terminal locations (poles or [[serving area interface|pedestal]]s). This allows the telephone company to use or "[[provisioning (telecommunications)|assign]]" that pair to any subscriber near those terminal locations. Once that customer disconnects, that pair becomes usable at any of the terminals. In the days of [[party line (telephony)|party line]]s, 2, 4, 6, or 8 users were commonly connected on the same pair which appeared at several different locations.

A bridge tap has no [[hybrid coil]] or other [[impedance matching]] components, just a “T” (or branch) in the cable.  Thus the bridge presents an [[impedance matching|impedance mismatch]].  The unused branch of the T is usually left with no device connected to its end, thus has no [[electrical termination]].  Both the tap and its unterminated branch cause unwanted [[signal reflection]]s, also called echoes.

[[Digital subscriber line]]s (DSL) can be affected by a bridged tap, depending on where the tap is bridged. DSL signals reflect from the discontinuities, sending the signal back through the cable pair, much like a tennis ball against a brick wall. The echoed signal is now out of phase and mixed with the original, creating, among other impairments, [[attenuation distortion]]. The modem receives both signals, gets confused and "takes errors" or cannot [[Synchronization|sync]]. If the bridged tap is long, the signal bounces back only in very [[attenuation|attenuated]] form. Therefore, the modem will ignore the weaker signal and show no problem. 

Line in bridge tap technology can be much less performing caused to the high attenuation added and to the length of the cable itself.

Bridged tap technology does not add latency. But it affects the performance of the line in general, it affects the bandwidth a lot.

A bridge tap can also be referred to as a "multiple" or a telephone pair "in multiple".<ref>Newton's Telecom Dictionary 23rd Edition 2003, Newton, Harry; p110</ref>

==References==
{{Reflist}}

==External links==
*{{cite web|url=http://www.vonl.com/support/faq/loadcoils.cfm |title=An Introduction to Load Coils and Bridge Taps |accessdate=2010-09-07 |url-status=dead |archiveurl=https://web.archive.org/web/20071115150145/http://www.vonl.com/support/faq/loadcoils.cfm |archivedate=2007-11-15 }} 

*{{cite web|url=https://www.thebroadbanddoctor.com.au/what-is-a-bridge-tap/ |title=What is a Bridge Tap?}} 

*{{cite web|url=https://www.pcmag.com/encyclopedia/term/bridged-tap|title= Definition of bridged tap}}

*{{cite web|url=https://www.infobloom.com/what-is-a-bridge-tap.htm|title= Bridged tap definition with photo |date= 28 November 2023 }}

[[Category:Local loop]]
[[Category:Signal cables]]