Phone Line Interfacing - FCC Part-68

mpm · 2008-05-20T02:16:24+00:00

I'm on a data-collection project, and the terminal will download viaPOTS.My question is: We're using the MultiTech Socket Modem (v.34, becauseit's low cost).In the documentation, they show several ways to interface to the phoneline.We will have a choke in-line for the tip and ring for common-mode.And a resettable fuse. So far, so good.But I have a question:MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),with one set each on both the tip and ring. The other side goes to"FGND". Any idea what this means, as it's not referenced anywhereelse in the document??I am assuming Earth ground, or at least some ground other than thepower supply ground driving the rest of the circuity. (There is alsoan analog ground for the modem speaker - which we're notimplementing...)Our box will be just that: A plastic box with a membrane keypad, anLCD, a 9VDC 2-conductor wall-wart power supply, and of course, anRJ-11 for the phone line. There will not be an earth-groundedconductor.Should we bother with the (Y2-rated safety) caps and sidactor(transorb) protection, or just go with the common mode choke andinline fuse? What is "safe", if anything, to connect to powersupply ground? Will the choke & fuse only arrangement pass FCC -68requirements?Thanks. (Seems like ages since I did any work with embedded dial-upmodems!)-mpm

May 20, 2008 21 Replies

Rate this thread:

David Lesher 18 years ago

You're dealing with the telephone company. We are not subject to city, state, or federal legislation. We are omnipotent.

Ernestine the Telephone Operator

A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that\'s close........[v].(301) 56-LINUX Unless the host (that isn\'t close).........................pob 1433 is busy, hung or dead....................................20915-1433

Vote

Michael A. Terrell 18 years ago

Woodpeckers destroyed the top 12 inches of the meter pole at my last house. It was a new pressure treated pole that is very hard to drill, yet the damn birds would hammer away at it all day while we were at work, till the top separated. If the break had been two inches lower, we would have had to buy another pole.

http://improve-usenet.org/index.html If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm Sporadic E is the Earth's aluminum foil beanie for the 'global warming' sheep.

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required