miket@brspyr1.BRS.Com (Mike Trout) (05/09/89)
I'm seeking microwave transmitters of certain frequencies and need some assistance. I recently purchased a Sears garage door opener transmitter (Model 53708) which I assumed would have the frequencies I need. Unfortunately, it appears to be frequency-adjustable, with no indication of what the possible frequencies are. The chip used is a TI TX8835 N 96856. It is connected to a 9-dipswitch unit with 3 positions per switch. I'm assuming that this allows certain pins on the chip to be placed high, low, or neutral. As there are thousands of possible combinations, I have no way of finding out what the possible frequencies for this chip may be. I'd greatly appreciate it if someone could e-mail me some information about this chip; specifically, what frequencies it can produce and how certain pins need to be tied to achieve them. Many moons ago I had access to chip specs manuals that would give me this information, but, alas, no more. Please e-mail rather than post. Many thanks in advance. -- NSA food: Iran sells Nicaraguan drugs to White House through CIA, SOD & NRO. ~~~~~~~~~~~~~~~~~~~~~~~~Michael Trout (miket@brspyr1)~~~~~~~~~~~~~~~~~~~~~~~~~ BRS Information Technologies, 1200 Rt. 7, Latham, N.Y. 12110 (518) 783-1161 "God forbid we should ever be 20 years without...a rebellion." Thomas Jefferson
greg@bilbo (Greg Wageman) (05/10/89)
In article <5847@brspyr1.BRS.Com> miket@brspyr1.BRS.Com (Mike Trout) writes: > >The chip used is a TI TX8835 N 96856. It is connected to a 9-dipswitch unit >with 3 positions per switch. I'm assuming that this allows certain pins on the >chip to be placed high, low, or neutral. As there are thousands of possible >combinations, I have no way of finding out what the possible frequencies for >this chip may be. This is admittedly just a guess, but is based on knowledge of my own garage-door transmitter. The dipswitches probably don't alter the frequency at all, but control some sort of code modulated onto the carrier. This is supposed to provide greater security and prevent a would-be-thief from simply driving up to your house and blasting selected frequencies at your garage until the door opens, or simply carrying a number of common door-opener transmitters and trying them until one works (don't laugh, it happens). The number of possible codes in my case is 2^10 (1024), since there are 10 dipswitches. The frequency is most likely determined by a crystal oscillator. There's probably a tuning coil with a powdered-iron slug for tweaking it, although not all designs have this. Some only have fixed inductors and a small trimmer capacitor for matching with the printed circuit loop "antenna". Longish .signature follows. Skip now, or don't complain. Greg Wageman DOMAIN: greg@sj.ate.slb.com Schlumberger Technologies UUCP: ...!uunet!sjsca4!greg 1601 Technology Drive BIX: gwage San Jose, CA 95110-1397 CIS: 74016,352 (408) 437-5198 GEnie: G.WAGEMAN ------------------ "Live Free; Die Anyway." ------------------ Opinions expressed herein are solely the responsibility of the author.
wiz@xroads.UUCP (Mike Carter) (05/10/89)
Regarding the garage door opener question: I highly doubt that the dip switches CHANGE the FREQUENCY. They, as with 99.9% of the rest of automation products, change the pulse count or CODE sent to the receiver. The receiver is SET at a FCC approved frequency. Normally a company receives 1, maybe 2 frequencies to run their production on with garage door openers. It is then up to engineering to develope a smei-fool proof (hah hah ;-) way of discerning the owner from the guys next door. If you change the dip switches, you are changing the code sent via the oscillator to the receiver. You must then change the code at the receiver to match what your transmitter is set for. If they indeed DID change frequency, 9 dip switches would enable you to go almost anywhere within the spectrum. Like I said...I doubt it. The FCC wouldnt approve. Enjoy! -Mike -- ============================================================================= = Mike Carter N7GYX, Phoenix AZ| Q: Why did the Chicken cross the road ? = = hplabs!hp-sdd!crash!xroads!wiz| A: To ESCape the Main Menu . = =============================================================================
parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S) (05/11/89)
garage door opener, Heath, believed to made by Linear Electronics, pcm
[GDP3309-A]_________ 310.0000____- (magazines)
garage door opener, Linear Electronics, used with Raynor openers, pcm
[DT]________________ 310.0440____ch A (B. Parnass)
garage door opener, Sears, made by Chamberlain, pcm
[139.664030]________ 389.3000____- (others)
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Bob Parnass AJ9S, AT&T Bell Laboratories - att!ihuxz!parnass - (312)979-5414