Hardware design questions

[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.