Adam Pollak
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Federal 550-AT Naming Convention

Sat Nov 14, 2009 1:37 am

I was going back trying to remember what the source was of the name "550" or "550-AT" for the dual-headed, rotating, dual-tone Federal siren, such as in Calhan, CO. The reason I ask is that I have something mentioning various warning devices (without pictures) and one of the listings is:

Federal Sign & Signal Corp. 500-DHTT Horizontal axis, bidirectional, 670 & 450 cps

DHTT would presumably be Dual-Head (DH), Dual-Tone (TT). The listed frequencies work out to essentially a 12/8 port siren, which is what the Calhan, CO siren sounds like. "TT" and "T" seem to be naming conventions used throughout various years by Federal. Most literature I've seen uses on "T" for dual-tone, but I have seen the "TT" before. Notably, Dane County, WI lists some of their sirens as "T" and some as "TT". Do any of you have more information on sirens like the Calhan, CO one being referred to as either a 550 or 500-DHTT?
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coop866
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Sun Nov 15, 2009 1:35 am

Dane County lists theirs as 500-AT-240's.

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Sun Nov 15, 2009 7:07 am

coop866 wrote:Dane County lists theirs as 500-AT-240's.

I don't think Adam is specifically talking about the 500 series sirens in Dane County. I distinctly remember seeing a Model 2TT on that list, and it being discussed in years past.

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Matt
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Sun Nov 15, 2009 2:18 pm

I saw the 7TTT on the list and I went out and recorded it if anyone is interested. I'd have to go dig up the tape though.
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coop866
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Sun Nov 15, 2009 2:38 pm

videogamer wrote:I saw the 7TTT on the list and I went out and recorded it if anyone is interested. I'd have to go dig up the tape though.
I went to see it too. Did it sound different then any 7T? It doesn't
look different.

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Matt
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Sun Nov 15, 2009 2:39 pm

coop866 wrote:
videogamer wrote:I saw the 7TTT on the list and I went out and recorded it if anyone is interested. I'd have to go dig up the tape though.
I went to see it too. Did it sound different then any 7T? It doesn't
look different.
I did not hear it but the ports looked the exact same. I just imagine this is all a huge typo because it also said my model 2 was from 1907 (but that might be still debatable)
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Fri Dec 23, 2011 10:19 pm

I'm going to bump this topic rather than posting new thread with this question. It's still never been answered to my knowledge, and I'd really like to know.

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Archon
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Sat Dec 24, 2011 5:10 am

coop866 wrote:Dane County lists theirs as 500-AT-240's.
500 A Means newer version versus the older style T dual tone 240 means running on 3 phase 240Volt

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500AT
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Sat Dec 24, 2011 6:44 pm

As I understand it, during the second term of the Eisenhower Administration in the White House, in the late 1950s a lot of changes were made to the Defense Civil Preparedness Agency (DCPA). One of them was the decibel/size ratings used on sirens for Civil Defense purposes versus those for civilian (fire) use. Federal Signal Corp., responded and used a different naming convention for CD sirens from roughly 1958 - 1970. However, they didn't always differentiate whether the siren was single or three-phase, as in the past. This was something the customer had to write on the order form.

During the Nixon Administration, starting around 1969-1970, the DCPA went back to rating sirens based on size: ie, A, B, C, D, etc. Federal followed suit going back to their older model designations. The Model 500SH TT, became the Model 500AT or 500BT. This eliminated any problems with the power phase of the motor when ordering from the factory.

From what I understand, the Model 500DH TT or later on known as the Model 550, was produced in two production runs. The first was in 1957-1958, while the second run was in the mid-1960s with improved sound projectors. This siren was designed to compete against the rotating dual-head HOR "Super Sirex."

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Ron W.

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Re: Federal 550-AT Naming Convention

Mon Jul 30, 2018 10:09 am

...while the second run was in the mid-1960s with improved sound projectors.
So the on in Callahan, CO is the 1st Gen, isn't it?

Any pictures of the second manufacturing run aka the 2nd Gen?

Sorry for bumping.
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