Most of the other smoke detectors on the market at the time where what we refereed to as high hats which stood 5-6 " off ceiling while the low profile ESL was 2"
My customers like many other alarm company customers wanted the lower profile units they just looked better and while some of the ESL smokes I installed have behaved and never falsed this was not the normal seems they worked for a couple years and then nothing but false alarm problems.
So like other company's I put the practice in place of if an ESL smoke falsed it was replaced with a System Sensor smoke which where very stable.
In the 90's ESL was bought and sold several times and they came out with a new design suppose to stop false alarms and while they had a better track record they still had problems the few I tested again some worked fine others just falsed. So I will no longer install them .
The units are still made but now they have had to have a major recall of units made in 2014 after it was found they will not activate in some cases.
ESL, Interlogix Hard-Wired Smoke Alarms Recalled Due to Failure to Alert Consumers of a Fire
Recall SummaryName of product: ESL and Interlogix brand 400/500 series smoke detectors
Report an Incident Involving this Product
UnitsAbout 141,000 in U.S. and 13,000 in Canada
DescriptionThis recall involves thirty-three models of the 400 and 500 series Edwards (ESL)-branded and Interlogix smoke detectors hard-wired into a security system. Edwards and Interlogix smoke detectors are identical. The 2-wire or 4-wire detectors are round, white and measure 6 inches across by 2 inches high. The smoke detectors were made for professional installation and used primarily in commercial buildings, schools, hotels/motels, apartments, dormitories and homes as part of the fire alarm system. Recalled units have date codes 13084 through 14059 with the first two digits representing the year, for example: 13 for 2013 and 14 for 2014; and the last three digits representing the day of the year, for example: 084 is the 84th day of 2013, which is March 25, 2013. The initials ESL, the date code and one of the following model numbers are printed on a label on the back of the detector’s cover and on the product’s packaging.
400 series: 429AT, 429C, 429CAD, 429CRT, 429CST, 429CT, 429CTAD, 449AT, 449C, 449CRT, 449CSRH, 449CSRT, 449CST, 449CSTE, 449CT and 449CTE.
500 Series: 511C, 518C, 521B, 521BXT, 521B-10PKDMP, 521B-10PKG, 521BXT-10PKG, 521BXT-DMP-10PKG, 528B, 528CRXT, 541C, 541C-10PKG, 541CXT, 541CXT-10PK and 548C.