Bob, first, say "Thank You" to the French who made the current limiter the political price for joining the CTR21. Second, there is nothing You can do about Ohm's law. But relax: Review clause A.4.7.1 for the DC template test procedure which allows one minute cooldown time in quiescent condition between the tests. The second test to look at is return loss. Be sure to have a medium power transistor in the DC holding circuit which can dissipate sufficiently otherwise You will not survive due to thermal runaway of Your circuit. The extreme 50V 230ohms feeding is not very realistic for real life. Robert Robert Pausch, Environmental and Regulatory Compliance Compaq Computer EMEA bv, Munich Tel: +49-89-9392-2352 FAX: +49-89-9392-2336
> -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Friday, March 12, 1999 2:27 PM > To: [email protected] > Cc: [email protected] > Subject: TBR 21- 60 mA max. loop current > > > Subject: TBR 21- 60 mA max. loop current > > > Hello all, > > I am brand new to this list.....so please be gentle 8-) > > My concern is the possible increased power dissipation re- > quired by the terminal equipment (TE) when connecting to > the EU PSTN. Assuming the worst case of: the test model > 50.0V (could even be higher in practice) battery and 230 > Ohm battery feed resistance, and short (co-located) loops, > this equates to 50.0 -.06A x 230 = 36.2V across the TE T,R > port. Now, since Ohms (not to mention Kirchhoff's) law has > yet to be repealed, results in a maximum per port power > dissipation of P(T,R) = 36.2V x .06A = 2.172 Watts! This > is about (in our case) 3x the heat dissipation that we ob- > serve when interfacing the North American 48V/460 Ohm battery > feed model. > > Has anybody out there also "taken the heat" 8-) and if so, > been able to defy Mr. Ohm and/or Mr. Kirchoff and somehow > dissipate less heat (and still meet TBR 21, of course)? > > Thank you...cool it...and.. > > cheers, > > bob lee > > >
