Vic, Once again you're right. I always forget telecom system engineering practices evolved in a different direction than electronic engineering. A good example of that is the different terminology used. i.e. metallic, longitudianl, return loss...etc.
In the 1960's I designed a ringer circuit for a Euro company that used thyristors and started the ring signal at zero. It wasn't as good as an exponentially rising signal, but it didn't generate all the multiplied frequency components that present ringer circuits do. I guess the main reason CO ringer circuits have survived so long is due to low cost and they have little effect on voice transmissions. We presently worry so much about generating extraneous frequency components and passing approvals when designing terminal instruments it is easy to forget how the system evolved. Thanks for the reality check. Regards, Duane ______________________________________ On 1 Apr 1997, Victor L. Boersma wrote: > Duane, > > > You wrote: > > >>As much as U.S. telecom practices are maligned by engineers and PTT's > outside of this country, this kind of signal generation in not allowed. > Part 68 is a double edged sword, it also controls the approval of CO > equipment. << > > > > (1) Telecom systems where not designed, they "evolved". This is one of the > major > cultural differences between data processing networks and practices and > telecom networks and practices. Because of this characteristic, you'll > find > a lot more slop in telecom systems design than in data network design. > That spills over in the terminal design and indeed puts more of a burden > on the > designers of terminals for telecom networks. > > This is changing as indeed more and more of the network is being > redesigned to > serve the global information infrastructure, but there is on heck of a > lot > of the > "evolved stuff" still out there. > > (2) Part 68 of the FCC Rules and Regulations does NOT control approval of > Central Offce > equipment. Approvals of Central Office equipment are strictly an issue > between the > buying telephone company and the selling supplier. You also will find > that > the > standards developed by Committee T1, to describe the interface between > the > public > switched network and the customer premises, have mandatory statements > only > on the part > of the customer premises, not on the part of the public network. There > were good > solid reasons for that. > > > Ciao, > > > Vic > >
