The Sensitive Relay

Splitpair

Back in the past a company named Alarm Device Manufacturing Company (ADEMCO) was in the business of developing and supplying electrical alarms systems to security companies.

One of the first problems they had to solve was powering the system as the design they used was a closed loop protective circuit which required continuous power from a 6 VDC string of dry cells and at the time the highest amp hour dry cell was the Number 6 which was rated at 1.5 VDC / 13.5 Ah,

To achieve a long battery life of at least 6 months or more they developed the Sensitive Relay, a relay which at 6 VDC would only draw .008 amps into a short.

[http://www.channel1images.com/BBF/SR1.jpg]

[http://www.channel1images.com/BBF/SR2.jpg]

[http://www.channel1images.com/BBF/SR3.jpg]

It was more like clockwork than what is now considered a mechanical relay, but it worked and worked very well.

HooRU

Very intersting, I never knew.

Splitpair

HooRU Very intersting, I never knew.

It’s uncommon to have a 6 VDC relay with a 750 ohm coil, normally a 6 V relay would have something like a 40-50 Ohm coil.

real_aurgathor

Digikey lists a bunch of 6 VDC relays with a 1029 Ω coil, though none of those are in stock.

Here is a data sheet for some: https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1782/TX-S_Series_Rev_Sep_2010.pdf

And the relevant section:

Splitpair

real_aurgathor Digikey lists a bunch of 6 VDC relays with a 1029 Ω coil, though none of those are in stock.

They seem to have been out of production for quite awhile, plus they would never do the job as the contacts would be fried the first time the alarm system was activated.

real_aurgathor

Splitpair

Splitpair They seem to have been out of production for quite awhile,

I’m willing to bet that the ADEMCO relay has has been out of production much longer than the Panasonic relays, and as per data sheet, only the “self-clinching terminal type” has been discontinued, and the rest is still orderable.

Splitpair plus they would never do the job as the contacts would be fried the first time the alarm system was activated.

Current wasn’t part of the original claim.

Splitpair

real_aurgathor I’m willing to bet that the ADEMCO relay has has been out of production much longer than the Panasonic relays,

Who cares or do you fail to understand the need that it filled?

None the less it was amazing for it’s day and was not only sensitive and low current it’s contacts could handle way more current than any of those modern Panasonic relays ever could, a restriction rendering them useless for the intended applications of the ADEMCO sensitive relay.

Applications such as the single stick relay alarm system.