Jam signal

Jam signal

In telecommunications, a jam signal is a signal that carries a 32-bit binary pattern sent by a data station to inform the other stations that they must not transmit. In CSMA/CD the maximum jam-time is calculated as follows: The maximum allowed diameter of an Ethernet installation is limited to 232 bits. This makes a round-trip-time of 464 bits. As the slot time in Ethernet is 512 bits, the difference between slot time and RTD is 48 bits (6 bytes), which is the maximum "jam-time".

This in turn means: A station noting a collision has occurred is sending a 4 to 6 byte long pattern composed of 16 1-0 bit combinations. Note: The size of this jam signal is clearly beyond the minimum allowed frame-size of 64 bytes.

Some notes about jam signals include the following:

#In carrier sense multiple access with collision detection (CSMA/CD) networks, the jam signal indicates that a collision has occurred.
#In carrier sense multiple access with collision avoidance (CSMA/CA) networks, the jam signal indicates that the sending station intends to transmit.


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  • Jam — Jam, v. t. [imp. & p. p. {Jammed} (j[a^]md); p. pr. & vb. n. {Jamming}.] [Either fr. jamb, as if squeezed between jambs, or more likely from the same source as champ See {Champ}.] [1913 Webster] 1. To press into a close or tight position; to… …   The Collaborative International Dictionary of English

  • Jam — Signal Nach der Entdeckung einer Kollision beim CSMA/CD Zugriffsverfahren auf den besetzten Kanal geschicktes Signal …   Acronyms

  • Jam — Signal Nach der Entdeckung einer Kollision beim CSMA/CD Zugriffsverfahren auf den besetzten Kanal geschicktes Signal …   Acronyms von A bis Z

  • jam — jam1 [ dʒæm ] noun * ▸ 1 sweet sticky food ▸ 2 line of stopped vehicles ▸ 3 blockage in machine ▸ 4 difficult situation ▸ 5 music 1. ) count or uncount a sweet sticky food made from boiled fruit and sugar, that is usually spread onto bread:… …   Usage of the words and phrases in modern English

  • Jam 1575 — Infobox Radio station | name = Jam Radio town = area = Kingston upon Hull branding = slogan = Spread it on your bread, stick it in your ears! airdate = 1983 as URH frequency = formerly 1575 AM KHz,now online format = Student Radio power = N/A… …   Wikipedia

  • jam */ — I UK [dʒæm] / US noun Word forms jam : singular jam plural jams 1) [countable/uncountable] a sweet sticky food made from boiled fruit and sugar that is usually spread onto bread strawberry jam a jar of jam a jam tart 2) [countable, usually… …   English dictionary

  • signal — {{Roman}}I.{{/Roman}} noun 1 sign/action/sound that sends a message ADJECTIVE ▪ clear, unmistakable ▪ agreed, prearranged ▪ conflicting, confusing, contradictory …   Collocations dictionary

  • jam — [[t]ʤæ̱m[/t]] jams, jamming, jammed 1) N MASS Jam is a thick sweet food that is made by cooking fruit with a large amount of sugar, and that is usually spread on bread. [mainly BRIT] ...home made jam. (in AM, usually use jelly) 2) VERB If you jam …   English dictionary

  • jam — 1. noun /d​͡ʒæm/ a) A sweet mixture of fruit boiled with sugar and allowed to congeal. Often spread on bread or toast or used in jam tarts. I’m in a jam right now. Can you help me out? b) A difficult situation. She was married when we first met… …   Wiktionary

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