Electronic Alarms and Home Security Devices - Fire Sensor - 135 degrees needed

We have both smoke and fire sensors in our home. The fire sensors tie into the central station. One of the fire sensors failed. It appears to have a small dent in it. They are about 1 1/2" in diameter and have two double screw terminals on the back. The unit is about 1" thick. They are normally open and close on 135 degrees heat. I need to find a source for these for replacement. They are 30 years old and now I do not trust them after the alarm today. It was lucky we were home so we did not bother the fire dept. Lucky. Anyone know a source for the devices?
Thanks

That is an older design. I think that Edwards still makes those "hockey puck" style heat detectors, but most people are replacing them with the slightly larger Rate of Rise heat detectors.

Any suggestions where I can get them? I need 11 units.
Thanks

If there is a local fire alarm installation company, they may sell them to you over the counter. Otherwise, online search using the phrase "rate of rise heat detector".

I picked one hit at random; try this for an example (http://www.home-technology-store.com/detail.aspx?ID=2498).

Do you suggest a 135 degree heat detector or a combo unit? I also see 135 fixed and rate of rise. We have the old style throughout the house making up 3 fire zones that tie to the central station. We have them in the basement near the heating unit, in the garage, kitchen, halls and in all bedrooms. Is a mix of types preferred?

The rate of rise + fixed is the better design, as it will react to the rapid increase in temp for an incipient fire better, and will catch a fire when it is smaller (in general).

Remember, these things are not _life safety_ devices; they shouldn't be used where a smoke detector is a better choice.

We have 11 temp sensors and 11 smokes in the house (also have 3 COs by MA law. The smokes are inter-connected but do not go to the central station. I plan to the dual fixed and rate of rise as replacements. Thanks for your advice.