Elk M1 keypad - 4 conductor?

[swill]

Hello all! First post. Wanting to upgrade our home's Networx system that is broken and upgrade it to something more modern like the Elk M1. However our home was wired with 4 conductors going to existing keypads. I can't run new Cat 5. Will 4 conductor work with the Elk M1 keypads?

Thank you,
Scott
Atlanta, GA

 

[KenN]

Yes. The keypads are 4-conductor RS485. Extra conductors are only need if you wish to expand the keypad's functionality to include a card reader or extra zone contacts from the keypad.

 

[Del91574]

Ken's answer is missing some key details.

As long as you don't intend on tying anything on to the M1's input or output at the keypad, you don't need more than 4 conductors at the keypad, you would be limited to 2 branches on the bus running back to the M1.

If you have multiple keypads and have the possibility for more expanders, etc. then you'll need a DBHR to have more than 2 branches using 4 conductor wiring, otherwise all the other bus devices will need a minimum of 6 conductors

 

[jpmargis]

you would be limited to 2 branches on the bus running back to the M1.

This needs a bit of clarification. The limitation of two branches is for the data bus at the M1. You can branch off once at the keypad or any other device until you reach the distance limitation. Just be sure to set the terminators correctly.

 

[Del91574]

JP, your statement, while true, is missing a key point.

On the M1, you can run 2 DBHR's, which will give you 4 supervised branches each, capable of 2 "splits", so 8 terminated home runs per DBHR, so you can have 16 individual home run "splits" prior to worrying about how the bus is truly wired or it's topology, since it's doubtful that a house would have more than that many home runs that need to be connected to the bus.

 

[jpmargis]

My point was that stating "you would be limited to 2 branches on the bus running back to the M1" implies that the branching can occur away from the M1 when in fact it must occur at the M1. Ditto for the M1DBHR. If there is branching, it must occur at the M1DBHR. Creating stubs on a high speed RS-485 bus can result in waveform distortion and a very difficult to troubleshoot system problem.

 

[tmbrown97]

jpmargis - I must admit - your previous post was unclear to me as well and lead me to believe you were saying something contradictory to your most recent one - I'm glad you cleared it up.