Garage door key switch

I'm the OP on this. Here's the current setup on this key switch:

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Yes. I guess I assumed (hoped) that the swtich was designed such that if it was removed, the wires would break away in some fashion that would leave them inaccessible from the front. At least, that's what I would have done. But of course I won't know until I remove it.

So there must be a part B that's the receiver. This is a Sears opener from 1972, and the mechanical box still works fine, but the original transmitters and receiver died long ago, and instead I use this set:

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I see that there is also a 318K available, a keypad which appears to use the same receiver. If so, that would be pretty straightforward. However, not having seen the 318K, it's not clear how secure it is. Does it simply transmit whatever you enter to the receiver, or do you set a specific code in the keypad? I know that both the T and R of the current setup have to have the dipswitches set the same way. Well, I'll need to look into that. It seems a lot of things that should be secure really aren't, starting with padlocks.

But I guess the basic question is whether I'd rather use a key or a keypad. It's basically for times when I need to give someone who doesn't have a clicker access to the house when I'm not there. And if secure, it seems the keypad is more convenient, and if it's done correctly, more secure. I assume all current construction uses keypads.

Reply to
Peabody
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This picture shows all I know about this switch:

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Are you saying I may have a problem removing the old switch? If there's a nut holding it from the back, it's unlikely I'll be able to get to that.

Reply to
Peabody

[snip]

Most of the digital keypads allow for you to set a "one time code" for such things as repairmen, deliveries, etc. You set your preferred code (4 digits) and there is also a programming code so you put in the one-time codes and changing your own code. For an older unit such as yours, you are looking at buying both the transmitter and receiver. They pair up without setting dipswitches, using a programming button not unlike the "WPS" button on WiFi routers.

Digital access (we use it for the home as well as the access door for the garage/shop.) is quite secure and if someone should get pass that they still have to contend with the alarm system.

Reply to
Unquestionably Confused

Hmm...This particular design looks like it's responsible for letting the garage door opener know that the door is down. IE: stop position sensor...

As, it's too small to be the safety reverse; I don't see how you'd break it if you happened to get in the doors way.

Monster,

What was it's function in the garage door opener?

Reply to
Diesel

Diesel brought next idea :

I assumed it was a gate in which an obstruction tab gets in the slot, like a travel limit sensor. VCRs eject mechanisms have similar shaped sensors. Without seeing where it is located, it is hard to guess.

Reply to
FromTheRafters

The manual for the 318K is off the page. There is only the four digit PIN. No one time codes.

Don.

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(e-mail link at home page bottom).

Reply to
Don Wiss

You'll have to check the documentation to find out for sure, but every one of these things that's decent that has been made in the last 25 years that I've seen has used pseudo random codes between the transmitter and receiver so that it's virtually impossible for a thief to intercept the communication and open the door. You have a 4 digit code, but that isn't what get's sent over the air. The transmitter and receiver are synched and what looks like a random number is transmitted from the keypad to the base unit in the garage. Because they are on the same pseudo random number sequence, the base unit knows what number should be coming for the next opening of the door. For example, if 34679495 opened it this time, then it knows 68830352 is what opens it next time. A thief intercepting the first one has no clue how to generate the next one.

I know that both the T and R of the

Well, that doesn't sound good, because dip switches was the old way, where there are only X number of codes with X being determined by the number of switches, 2^^X. That method isn't very secure at all, you just have to go through the possible codes one at a time, but then I've never heard of anyone who got broken into that way either.

The documentation you have for the units you already have should make it clear how it works.

Reply to
trader_4

Yes, what I have now is fixed key, set by 9 jumpers. There are videos on Youtube showing a guy using a modified Mattel OpenSesame toy that goes through all possible codes in about four seconds. It's actually quite interesting when he gets to the math behind it because you don't have to send all possible codes, just a small fraction of that.

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So I guess it's time to move into the modern world and replace my stuff with rolling code versions, including a keypad to replace the keyed switch.

Reply to
Peabody

I read something on the ole interweb related to reducing the number of keypad combinations that one would need to try. I have no way of confirming it's validity, but here it is anyway.

Supposedly burglars can tell which keys are used most often by their appearance - clean vs dirty, oily, etc. If you take that information and combine it with knowing how many keystrokes a particular model key pad uses, you can narrow the combinations down to only the various combinations of (for example) 2, 6, 8, and 9.

That still seems like an awful lot of choices for a stranger to stand at your door trying, so it may be nothing more than scare tactics. I think I'll look at my keypad tonight and see if I can tell anything from the look of the keys. Knowing my code will help me narrow in on the keys I use most often so if I can't see any difference, I doubt a burglar can.

Reply to
DerbyDad03

That was very interesting. I knew it can be done, but wondered what you'd use for hardware, how much development it would take, etc. This shows it's not trivial, but not all that hard and that toy is a convenient hardware platform. And I see what you're saying, the system has holes in it, where you can hit it with codes with no delay and it uses a shift register comparison, which cuts down the codes you need to send to find the right one.

He says he can get into a door with 12 bits in less than 10 secs. You have 9 bits, even worse. Still, IDK anyone who has had a burglar get in that way. It's clearly a vulnerability though and the pseudo random code type are orders of magnitude more secure.

Reply to
trader_4

Or change the PIN every once in a while to the clean keys.

Don.

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(e-mail link at home page bottom).

Reply to
Don Wiss

I see.. good point, interesting comparison. It's been a long time since I've opened a VCR. [g]

Reply to
Diesel

Ahh...

Is that a good thing?

Reply to
Diesel

Diesel laid this down on his screen :

Someone else's post has reminded me that the supply and take-up reels on the deck also has these to detect reel RPMs. When you rewind using the deck instead of a cheap rewinder it "knows" to slow down near the beginning so as to not slam stop and possibly break the tape.

There are many applications for these.

Reply to
FromTheRafters

Yep. I've seen them used in other devices including gate openers...

Reply to
Diesel

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