Roland M48 System with generic PoE swtich

[Cotton]

Hi,

Is anyone using the M48 without the S4000D?

We've only just got one M48, and are only likely to have one for a while, so I don't want to buy the S4000D. I know Roland reccomend a PoE injector from TREND.

Has anyone had any success with a normal Power over Ethernet switch?

Appreciate your help. Justin.

[Cotton]

Just thought I would follow up on this, in case it helps anyone else out.

The M48 uses 'Alternative B' or 'Mode B' Power over Ethernet. This mode puts the power on the 4 spare wires in the cat5 cable. Most PoE switches use 'Mode A', where power is put on the 4 data lines in the cable.

Generally, Powers supplying devices can use mode A OR mode B, while powered devices need to be able to receive power by BOTH methods. So the M48 is not a normal PoE device.

This explains why PoE injectors work - they simply pass the 4 data lines through uninterupted, and add power onto the spare wires.

Justin.

[TomandPen]

I have used the TrendNet TPE-101i with success. However, it now appears that the 101i has been replaced with the 111g. I tried using those last week and had to return all of them. Even with the same specs as the 101i, they didn't work. Trendnet said I must have gotten a defective unit. All 3 of them.

Where did you get your info on the mode A and mode B? I hadn't heard that, but it would explain why only certain PoE injectors would work with the Roland unit. I have a PoE switch that doesn't power up the M48 either. The TPE-101i is the only unit I've found that would work.

[Cotton]

The general mode A / mode B PoE information is available anywhere on the internet.

The information about the M48 I recieved by email directly from an engineer at Roland.

Odd that the TPE-111G(I?) doesn't work... It is the one reccomended by Roland. Perhaps send an email to Trendnet asking what pins the power is injected on?

I borrowed an injector from my work, normally used for VoIP phones.

You could build a simple injector I suspect simply with a 48 V 15W power supply and a junction box.

[TomandPen]

It was odd that none of the 3 TPE-111's I purchased worked. I simply unplugged one of the functioning TPE-101's and plugged in the TPE-111 and got nothing. I've been looking for another PoE injector that would work. I just don't want to invest in something that I can't return since it appears that the M-48 is rather picky about how it receives its power. If all I have to do is find a PoE injector that operates in Mode B, I'm set. Thanks for the info.

[Cotton]

I guess one thing to consider is cable length. The injector I am using will not drive a long cable - too much voltage drop. I have to have the injector at the M48 end.

Devices using Mode A PoE use a transformer, (expensive), to both inject and extract power from the data lines. This is a more complicated method than mode B, where power is simply applied to the two unused pairs in the cable. It is possibly slightly more robust as well, since you aren't loading the data lines with a transformer.

So, my understanding is that most injectors inject using mode B. They simply pass the data lines straight through, and then inject power on the unused wires in the cable. To actually interrupt the data lines and inject power is a whole lot more involved, requiring much more complicated electronics.

It would be very interesting if you could find out what pins the Trend device puts it's power on. The pin layout of mode A is: Power +: pin 3 and 6, Power -: pin 1 and 2
*
On the ohter hand, the pin layout of M-48 is mode B: Power +: pin 4 and 5, Power -: pin 7 and 8

[jwbroadhead]

Hoping to clarify some questions for you.
The M-48 is a mode B device meaning it takes power on pins 4-5 and 7-8. (Mode A assumes power on 1-2 and 3-6)

A typical powering device decides whether to provide mode A or B to an attached device.
However, many of these little “brick” injectors are not built “smart” enough and do mode A or B only.

So for these stand-alone units you have to ensure the right pins are providing power.

Thanks for bringing our attention to the TrendNet reference on our website and it was in fact pointing to the wrong unit.
The TrendNet TPE-111GI unit that replaced the TPE-101I switched to a Mode A power style.... so now does not work with the M-48... Only the 101I works.

Level One offers some solutions (POI-2002)
PowerDsine as well.

Same goes for switches. Just make sure they provide at least 15W per port under full load and can handle Mode B devices.

Although we know our Roland S-4000D Switch is more expensive than other switches, it does

• allow for full load of up to 8 - 15 and/or 25W devices
• has proper ethercon connectors for your RJ45 jacks so you don’t have to rely on those ugly plastic Cat5/6 jacks and the tabs that are guaranteed to break off
• nicely rack mountable
• status lights to indicate specific activity and power
• nothing "smart" about it so nothing to config or administer - just plug and play
  

A Power over Ethernet switch build for Pro Audio.

Trust that helps and sorry for any confusion.
Thanks too for your support of Roland product.

Best regards,
John Broadhead
Roland Systems Group

[Cotton]

Hi John,

Great to see you on the boards, and willing help out people using PoE injectors, rather than your S4000D.

Justin.

[jwbroadhead]

Happy to help with the technical explanation.
The only caveat, which is likely obvious, is that we are not able to provide support on any 3rd party products.
We can only offer opinion on what may or may not work based on a written specification after which if the user goes down that path they are "on their own".
That being said, a PoE injector is simple technology and some of our users have had success using them on that odd random run or that 1 extra one they needed in some other location.
We still highly recommend using the S-4000D for professional installations.

Trust that helps,
John Broadhead
Roland Systems Group