Login

***ident*** · 01-21-2014, 06:44 PM

The sound worked with VLC media player worked
That is quite soft, it sounds like RS485 noise. Check that the RS485 bus is securely terminated on both ends. The bus can still work if one wire is disconnected but may give noise. Does turning down the keypad volume reduce the noise?

gjb · 01-21-2014, 09:16 PM

[user=86]ident[/user] wrote:

Quote:The sound worked with VLC media player worked
That is quite soft, it sounds like RS485 noise. Check that the RS485 bus is securely terminated on both ends. The bus can still work if one wire is disconnected but may give noise. Does turning down the keypad volume reduce the noise?

By RS485 bus, do you mean the KA/KB connections? I have just checked these at both ends and they are making good contact. I have also disconnected the UCMs so that the keypad is the only device using the bus, but that didn\'t make any difference.
The keypad volume does adjust the volume of the interference, but it is not linear. At 0%, it is barely audible; by around 30% the interference has reached it\'s maximum volume; increasing the volume further only affects the level of the voice, not the interference. Does that suggest where the problem might be?

***ident*** · 01-22-2014, 07:37 AM

Yes, KA KB is t he rs485 bus
The noise is probably due to the interference from KAKB to the mic/voice signals

Make sure your KA/KB and MIC/VOICE are paired correctly in the CAT5
and the shield is grounded

gjb · 01-22-2014, 02:15 PM

I\'m going to rewire the keypad with STP (once the cable arrives), so will make sure that the shield is grounded. Hopefully that will solve the problem. Thanks.

cgiltrow · 11-21-2016, 05:43 PM

Hi,

Over and above the shielding, it is important to get the pairing right in order to get the benefit of the interference resilience that twisted pairs offer.

Am I correct in using the following pairs (for a keypad):

Pair 1: 12v+ and 12V-

Pair 2: KA and KB

Pair 3: Mic and 12V-

Pair 4: Voice and 12V-

Thanks,

Clinton.

***slychiu*** · 11-21-2016, 06:35 PM

Quote:Pair 1: 12v+ and COM
Pair 2: KA and KB
Pair 3: Mic and 12V
Pair 4: Voice and COM

we normally recommend
12V/COM
KA/KB
Mic/Voice
Spare

But I think your way may even be better as Mic and voice are paired with the power and return

cgiltrow · 11-22-2016, 10:43 AM

Thanks Chiu,

Can I just confirm (as you changed my post slightly), is it:

Pair 1: 12V and COM

Pair 2: KA and KB

Pair 3: Mic and COM (or MIC and 12V - as you showed in you last post)

Pair 4: Voice and COM

Clinton.

***slychiu*** · 11-22-2016, 10:52 AM

MIC and COM
Voice and COM

should be best