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  1. Join Date
    Dec 2004
    Posts
    228
    #11
    urban legend! car alarm works on different frequency than our cellphones. there's no way of 'tunneling' the signal of car alarm to that of cellphones signal and relaying it back to the car alarm's reciever in the car (unless you work out some kind of a repeater using your cell... but that's another matter). the case presented is pure myth imo.

    oopss... mods sorry for the double post.... paki delete na lang my first post.
    Last edited by amboy; October 12th, 2005 at 04:38 PM.

  2. Join Date
    Sep 2003
    Posts
    21,346
    #12
    Quote Originally Posted by amboy
    urban legend! car alarm works on different frequency than our cellphones. there's no way of 'tunneling' the signal of car alarm to that of cellphones signal and relaying it back to the car alarm's reciever in the car (unless you work out some kind of a repeater using your cell... but that's another matter). the case presented is pure myth imo.:
    This may be an urban legend, alright, but I once saw a feature on how carnappers work in Germany. I saw this in a German Channel/Cable TV. This maybe related to our topic.

    Carnappers use this Motorola Talkabout Walkie Talkies (I think they the T6226 model) to jam the frequency of these car alarm/devices that supposed to lock the car's doors. Ganito ginagawa nila. The guy would stand a few meters away from his target, holding his Motorola Walkie Talkie. He would wait for the car owner to come out, then once the driver would lock his car doors remotely, sasabayan niya ng pindot yung Walkie Talkie niya (yung "talk" button). The unsuspecting driver would just walk away, without checking the doors if it's really locked. Siyempre, tumunog na, naka-lock na. Yun ang alam niya. Pero, voila, hindi pala!

    Doon na e-entra yung "bida", and he can open the doors easily. Limas ang laman ng kotse mo!

    Pati yung field reporter, sinubok din yung MO na yun, at talagang gumana!

    Dito sa atin, marami akong nakikitang gumagamit ng mga walkie-talkies, this yellow, blue colored Motorola units, sa mga Malls. Yung mga can afford na bumili. Madalas gamit pa nga ng SM security force.

    Sabi ko nga, naku kung napanood ng mga "buwitre" ito, magkakaroon na naman ng bagong idea, kung pa'no mapapadali ang MO ng mga carnappers sa atin.

  3. Join Date
    Mar 2003
    Posts
    474
    #13
    hmm...funny, my dad and my sis tried this and it did work (i don't think they were kidding)...the car used was my sister's (vios)...the car was in the garage though but our garage is on a separate lot beside our house, separated by a firewall, they made sure that the remote was already not working at the said distance...maybe a case to case basis.

  4. Join Date
    Aug 2005
    Posts
    549
    #14
    i'll try this later.. SUN gagamitin ko

  5. Join Date
    Mar 2005
    Posts
    8,837
    #15
    d ba travelling hanggang 4khz lang max bandwidth frequency ng telephone line, that's why kahit anung ganda ng sound system mo sa bahay, kapag pinarinig mo sa
    kaibigan mo on another phone line, d din nya ma-appreciate yun sounds.

    although low-frequency lang ang keyless entry system baka pumasok sa limit na 4khz.
    but still how can the cellphone speakers transmit that signal at 1 foot distance?

    siguro dapat sagutin na ito ng mga ECE dito hehehe

  6. Join Date
    Mar 2005
    Posts
    8,837
    #16
    In order to allow more long-distance calls to be transmitted, the frequencies transmitted are limited to a bandwidth of about 3,000 hertz. All of the frequencies in your voice below 400 hertz and above 3,400 hertz are eliminated.
    correction 400 hertz to 3.4 Khz lang pala phone line

  7. Join Date
    May 2005
    Posts
    497
    #17
    Quote Originally Posted by oldblue
    d ba travelling hanggang 4khz lang max bandwidth frequency ng telephone line, that's why kahit anung ganda ng sound system mo sa bahay, kapag pinarinig mo sa
    kaibigan mo on another phone line, d din nya ma-appreciate yun sounds.

    although low-frequency lang ang keyless entry system baka pumasok sa limit na 4khz.
    but still how can the cellphone speakers transmit that signal at 1 foot distance?

    siguro dapat sagutin na ito ng mga ECE dito hehehe
    This is correct. The standard bandwidth for frequncy txmisn is 300 to 3400Hz on a telephone. As far as I know keyless entry tmiter/rcvr for the car uses the ISM band (around 2+GHz range) Most consumer electronics using txmter/rcvr fall within this frequncy band (notable examples: wi-fi, bluetooth, cordless phone, and microwave oven)

    Kaya pansinin niyo minsan pag nagpunta ka sa ortigas ng gabi, at sarado na ang mga opisina, minsan ayaw gumana ng transmitter na pampatay ng car alarm mo, dahil some of the alarm systems na gamit ng mga buildings sa ortigas also use the ISM band. Nakakainterfere siya sa alarm ng kotse mo

  8. Join Date
    Mar 2003
    Posts
    474
    #18
    Quote Originally Posted by laklak
    Kaya pansinin niyo minsan pag nagpunta ka sa ortigas ng gabi, at sarado na ang mga opisina, minsan ayaw gumana ng transmitter na pampatay ng car alarm mo, dahil some of the alarm systems na gamit ng mga buildings sa ortigas also use the ISM band. Nakakainterfere siya sa alarm ng kotse mo
    yup...experienced this once when i went to the podium...nagpark ako sa open parking between adb and the mall, when i was about to activate the alarm, ayaw gumana...took several tries pero na activate den. muntik ko na nga ireklamo sa casa yung alarm eh pero when i got home, it was working perfectly again!

  9. Join Date
    Mar 2005
    Posts
    8,837
    #19
    Quote Originally Posted by BeetOls
    yup...experienced this once when i went to the podium...nagpark ako sa open parking between adb and the mall, when i was about to activate the alarm, ayaw gumana...took several tries pero na activate den. muntik ko na nga ireklamo sa casa yung alarm eh pero when i got home, it was working perfectly again!
    ako naman I had a different experience, my dad had to literally pull me out of Metrowalk just to disable the alarm. my alarm remote had weak batteries and we forgot the location of the disable alarm button inside the car. we opened the car and we cant start it so hayun hinatak car ko.

  10. Join Date
    Oct 2004
    Posts
    2,315
    #20
    Kaya pansinin niyo minsan pag nagpunta ka sa ortigas ng gabi, at sarado na ang mga opisina, minsan ayaw gumana ng transmitter na pampatay ng car alarm mo, dahil some of the alarm systems na gamit ng mga buildings sa ortigas also use the ISM band. Nakakainterfere siya sa alarm ng kotse mo
    kaya pala sa ortigas ayaw gumana ng car alarm ko, ganun pala yun kala ko hindi ko na mabubuksan yun kotse ko

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