Hardware design questions

[sblair]

Originally Posted by jpk__

Can you confirm if the enttec unit has correct Command Port biasing? The enttec pro unit I have here doesn't.
Thanks, jpk

Good question. I can't recall for certain if it does. I'm pretty certain that Eric or one of the other more HW oriented guys will know.

The model I've always used is the RDM USB Pro. Because the same box can be used inline running the Sniffer app or as a Controller I'm thinking that it doesn't have the proper Command Port biasing otherwise it would likely be overterminating the line when used in series.

[jpk__]

Originally Posted by sblair

Good question. I can't recall for certain if it does. I'm pretty certain that Eric or one of the other more HW oriented guys will know.

The model I've always used is the RDM USB Pro. Because the same box can be used inline running the Sniffer app or as a Controller I'm thinking that it doesn't have the proper Command Port biasing otherwise it would likely be overterminating the line when used in series.

Is there anything in the standard about marking Command Ports with/without termination or can we safely assume anything on the command end marked E1.20 compliant must be a Command Port and thus is terminated correctly? Terminating with bias outside the box is a little tricky
Does anyone offer internally switched Command Port termination?
Thanks, jpk

[ericthegeek]

Originally Posted by jpk__

Is there anything in the standard about marking Command Ports with/without termination or can we safely assume anything on the command end marked E1.20 compliant must be a Command Port and thus is terminated correctly?

The standard says (emphasis added):
"Command ports shall include the line biasing network."

"Command ports may be designed with means to disconnect the line biasing network."

A command port that does not offer the line bias would not meet the standard. But, don't assume the BIAS is always present. The means to disconnect the bias may be internal jumpers that you can't see without opening up the product. A previous user could have disabled it without your knowledge.

Originally Posted by jpk__

Does anyone offer internally switched Command Port termination?

The DMXter4 uses relays to Add/Remove the BIAS network as appropriate. There's also a software override to let you remove the BIAS network for testing special cases.