[600MRG] Smoke Alarms I

[D.J.J. Ring, Jr.]

This one uses a 3.3 K ohm termination.

http://www.doityourself.com/forum/electronic-home-security-systems-alarms-devices/475438-smoke-detectors-nx8.html

73
DR

On Tue, Oct 21, 2014 at 4:10 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 21 Oct 2014 at 10:25, John Langridge wrote:
>
> > Can we get a detailed clarification on what "not terminated properly"
> > means?
>
> Probably not from me in this case. The reason is that such "termination" is
> completely dependent on what means is being used to connect the various
> parts of the system.
>
> In my experience with early cabled computer-networks, it specifically meant
> that any open connections at the ends of a particular "run" must be
> "terminated" in the characteristic impedance of the line which is being
> used.
>
> In the case of the early lines, that was RG-58 or similar, and thus the
> terminators were 50 ohm "dummy loads" installed within a male BNC
> connector.
>
> It also means that when a line is "looped" or "seriesed" through a device,
> like
> a router or hub, the output connection of that device must have a
> termination
> on its unused or unconnected output connections in order to prevent
> reflections which would corrupt data.
>
> A completely similar method is often used with in-home TV systems by cable
> from a central amplifier or connection to the TV-cable system: terminators
> must be used on any open ports or at the ends of open lines.
>
> I am certain the principle is identical in the case of hard-wired smoke
> detector systems, but since I am not knowledgeable about those, or how
> they are connected, nor with what, I cannot suggest how to do it.
>
> As someone here suggested, I would think that the thing to do is to go back
> on the installer.
>
> In what I would imagine are low-frequency systems, which those may be,
> leaving lines unterminated would not be noticable to the equipment, but
> most
> certainly would allow ingress of unwanted RF.
>
> I am sure there must be others here who would know far more about this
> matter than I.
>
> vy 73,
>
> Ken W7EKB
>
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