Roger, EIA/TIA 470A & FCC Part 68 both call for the same "loop simulator" to be used during testing, and some of the tests specifically state that they should be done at 20mA and 100mA. I have run into trouble with some CPE (telco slang for Customer Premise Equipment, i.e., a telephone device) that doesn't like 100mA of current! (Especially CPE that wants to "current-limit" to approximately 35mA, as some do.)
In the "real world," a typical digital CO will have a 52VDC battery feed, through a 200/200 Ohm feed coil. If a CPE were installed very close to a CO, so there is no significant loop resistance, and it was rather low in the FCC Part 68 permitted DC Off-hook resistance range, say, 100 Ohms, you would then see 52/(400+100)= 104mA, so the 100mA test current is not completely out of bounds. (But, very unlikely!) - John ------------------------------------ At 03:19 PM 11/20/96 MST, you wrote: >Hey all, > >Does anyone know off the top of their heads what is the max power draw >allowed on the Telco interface according to Part 68. > >I guess it is about time I get an updated Part 68! > >Thanks, > >roger >[email protected] > >"Democracy is the recurrent suspicion that > more than half of the people are right > more than half of the time." > - E. B. White > > ------------------------------------------------------------------ John Combs, Senior Project Engineer, ITS/TestMark Laboratories Email: [email protected] URL: http://www.testmark.com ------------------------------------------------------------------
