DSC 632 hybrid system: Multiple contacts on one transmitter

[glevin]

I recently purchased a DSC 632 hybrid system and found that the
instructions for the WLS925L-433 door/window transmitters say not to
put more than one contact on the external loop and "the wires
connecting the external device to the input terminals must not exceed
18 inches, provided that the resistance of the wire dies not exceed 100
Ohms."

I am replacing an old wireless system on which I had multiple
door/window contacts and about 40 feet of wire on one transmitter. I
measured the resistance of that normally-closed loop and got 18 Ohms. I
tested the transmitter often and it functioned flawlessly.

Why should there be a problem with multiple sensors on the external
loop of the DSC transmitter as long as the resistance is under the
specified 100-Ohm limit? Is DSC just trying to sell more transmitters,
or is there a better reason for the stated limitations? Parts of my
house are impractical to hard wire and I don't want to buy a separate
transmitter for each door and window if one transmitter can handle
multiple contacts.

I would appreciate any advice relating from folks with experience or
knowledge with this issue. Thanks in advance for your assistance.

 

[Frank Olson]

I recently purchased a DSC 632 hybrid system and found that the
instructions for the WLS925L-433 door/window transmitters say not to
put more than one contact on the external loop and "the wires
connecting the external device to the input terminals must not exceed
18 inches, provided that the resistance of the wire dies not exceed 100
Ohms."

I am replacing an old wireless system on which I had multiple
door/window contacts and about 40 feet of wire on one transmitter. I
measured the resistance of that normally-closed loop and got 18 Ohms. I
tested the transmitter often and it functioned flawlessly.

Why should there be a problem with multiple sensors on the external
loop of the DSC transmitter as long as the resistance is under the
specified 100-Ohm limit? Is DSC just trying to sell more transmitters,
or is there a better reason for the stated limitations? Parts of my
house are impractical to hard wire and I don't want to buy a separate
transmitter for each door and window if one transmitter can handle
multiple contacts.

I would appreciate any advice relating from folks with experience or
knowledge with this issue. Thanks in advance for your assistance.

The concern stems more from the fact that the extra wire in the loop tends
to act like an antenna which could result in false alarms. For the sake of
your customer's convenience and so as not to risk the wrath of the "RFI
Gawd", I'd suggest you consider follow their directions (even if it means
adding a few more transmitters). This having been said, I've got a couple
of units out there with more than one contact on them and wire runs of
around 15' (on average) with *zero* problems... Mind you, the could be
"muzzled"... ;-)

 

[Mark Leuck]

I recently purchased a DSC 632 hybrid system and found that the
instructions for the WLS925L-433 door/window transmitters say not to
put more than one contact on the external loop and "the wires
connecting the external device to the input terminals must not exceed
18 inches, provided that the resistance of the wire dies not exceed 100
Ohms."

You must have an old sensor, the new version increases that to 10 feet, you
can tell the old ones which had 4 tuning coils (2 red and 2 green), the new
version does not have these

 

[glevin]

Thanks for the responses. Last night I looked at the instructions for
the WLS907-433 door/window transmitters. For those it says any length
of wire is okay as long as the resistance is below 100 Ohms. Since they
are bigger and have more battey power, I imagine the WLS907's have a
stronger signal and maybe a bigger antenna than the WLS925's, though I
don't have the specs on output signal strength.

However even for the 907, the instructions say to connect only a single
contact to the external loop.

 

[glevin]

You must have an old sensor, the new version increases that to 10 feet, you
can tell the old ones which had 4 tuning coils (2 red and 2 green), the new
version does not have these

The transmitters don't have the red and green tuning coils but they do
have the 18" limit in the instructions. Maybe the instructions lagged
the design?

 

[Mark Leuck]

The transmitters don't have the red and green tuning coils but they do
have the 18" limit in the instructions. Maybe the instructions lagged
the design?

That wouldn't suprise me, I got that info from a DSC advisory and they were
very specific about the tuning coils so I'd say give it a shot