I can confirm the comments of Robert Pausch below. In 1997 I had a conversation with a French telecom engineer. He stated the problem was saturation of the feed inductors.
In late 1998 I had two conversations one with a French Telecom administrative person and the other with a French Telecom engineer. The admintratrive person stated current limiting was required period, but the engineer stated all the older equipment had been removed from service. As a consequence the current limiting requirement was no longer needed. He knew the solid state SLICs that replaced the older equipment had to limit the current to survive shorts and misuse. Duane >Ref: Feed inductors / Relay coils >The argument sounds powerful but is already obsolete! With the advent >of the new numbering scheme every switch of France Telecom is >electronic and does not have any feeding relays. It has already happened. >The current limiter is definitely a political requirement and will have to >go. >There is no excuse. >CTRs may only establish essential technical requirements. This opinion >was confirmed by a member of ATAAB commitee. >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: Monday, March 15, 1999 5:55 PM >> To: [email protected] >> Cc: [email protected] >> Subject: Re: TBR 21- 60 mA max. loop current >> >> In a message dated 3/15/99, [email protected] writes: >> >> > I Understand that the French PTT say that the Feed inductors / relay >> coils >> > used in their network saturate at 60mA +, when saturated no ac is passed >> so >> > transmission becomes highly attenuated. This was too powerful an >> argument >> > for allowing current to exceed 60mA in the TBR / CTR. >> >> >> Bill: >> >> Thanks for shedding some light on the rationale that the French used to >> defend >> the inclusion of the 60 mA requirement. I have heard various >> explanations, >> but this is the most believable one yet. >> >> It seems to me that eventually, the French network (already claimed to be >> one >> of the most modern in the world) will be fully upgraded to solid state >> feed >> circuits which contain their own current limiting. I would think that the >> feed coils which are in danger of saturating would only be associated with >> older, electro-mechanical central offices. Has there been any discussion >> of >> phasing out the 60 mA requirement at some point in the future? >> >> I recall that in their formal response to the proposed TBR 21, the UK >> included >> a comment that perhaps the 60 mA current limit could eventually be phased >> out. >> It seems to me that if enough vendors of terminal equipment complained >> about >> the 60 mA requirement, France might be persuaded to agree to a phase-out >> date. >> >> I might also add that while the 2 watt dissipation may be tolerable in >> most >> types of TE, it is particularly onerous for designers of PCMCIA cards and >> high >> density, multi-port cards. I think that most manufacturers of TE >> (including >> manufacturers located in France) would have an interest in eliminating >> this >> requirement. >> >> >> Joe Randolph
