Dorin, Excellent information. However, if my memory serves me, the ANSI spec forbids passing the DC voltage on to the customer equipment side of the demarcation point. In other words, if the telco is going to provide span power for repeaters or sealing current on a DS1 line they MUST install a T1 smart Jack type device that prevents the DC from being passed to a T1 DSU. The T1 smart jack acting as a CSU must loop the DC to keep the repeaters from dropping out. So it actually depends upon who owns the CSU (customer or phone company) as to whether the DC must be looped. Of course, if you do not loop the DC, the telcos will not buy it! Jim
>---------- >From: Dorin Gheciu[SMTP:[email protected]] >Sent: Friday, January 02, 1998 11:17 AM >To: [email protected] >Subject: Re: BOUNCE [email protected]: Non-member submission from >[Dorin >Gheciu <[email protected]>] (fwd) > >Hello Jim, > >Thank you very much for your excellent advice. Indeed, I found a similar >spec to the one you suggested, namely Bellcore TR 62411, that specifies >the same. I was confused since a more recent spec, namely ANSI >T1.403-1995 actually forbids the use of DC power: see section 6.5. >However, since our products should be compatible with older equipment as >well, your advice is excellent. > >Thanks again, >Dorin > >JIM WIESE wrote: >> >> The requirements for a T1 CSU are located in Bellcore TR-TSY-000312 >> Issue1, March 1988. Section 2.3 will give you the detailed answer your >> looking for, however the short answer is you do need to provide the DC >> path. The reason is that midspan repeaters will not function if the >> path is broken. This Bellcore document tells you everything you need to >> know about "DS1 interface connectors" (Bellcore's name for T1 smart >> jacks, T1 CSU's etc) needs to do. >> >> Jim >> >> James Wiese >> Regulatory Compliance Engineer >> ADTRAN, Inc. >> 205-963-8431 >> 205-963-8250 FAX >> [email protected] >> >> >---------- >> >From: Jon D Curtis[SMTP:[email protected]] >> >Sent: Thursday, December 18, 1997 9:59 AM >> >To: [email protected] >> >Subject: BOUNCE [email protected]: Non-member submission from >>[Dorin >> >Gheciu <[email protected]>] (fwd) >> > >> >From: Dorin Gheciu <[email protected]> >> >Subject: T1 CSU compliance >> > >> > Is anyone aware of a need to provide DC continuity >> >through T1 CSU's ? >> > >> >Before 1989, T1 CSU's used to be powered by access >> >providers. To accomplish this, the access provider >> >would send DC current that would loop back via the >> >center taps of the Tx and Rx transformers of the CSU. >> > >> >Although this requirement has been abolished, I was >> >advised by a colleague to still connect together the >> >center taps, since some Telco's may expect it, and use >> >it for "contact wetting". Unfortunately, it complicates >> >the surge protection of the CSU. >> > >> >Thanks, >> >Dorin Gheciu >> >Mororola ISG >> > >> > >> > RCIC - http://www.rcic.com >> > Regulatory Compliance Information Center >> > >> > >> > >> > > >-- >Dorin Gheciu >Senior Staff Engineer >Motorola ISG >Tel:(905)712-7556 Fax:(905)507-7200 >
