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From: jon_sree@world.std.com (Jon Sreekanth)
Newsgroups: comp.dcom.telecom
Subject: Re: How Do I Tell When...
Message-ID: <16736@accuvax.nwu.edu>
Date: 6 Feb 91 19:42:52 GMT
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X-Telecom-Digest: Volume 11, Issue 97, Message 10 of 10


In article <16525@accuvax.nwu.edu> zazula@uazhe0.uphysics.arizona.edu
writes:
 ....
[See previous message if you need to review the question.  PAT]

Regarding commercial units that do this (I've heard mention of a Radio
Shack box) Does anyone know what their REN is ?

Just yesterday, a consultant told me that the REN was calculated as a
worst case of several measurements, one of which was DC on-hook
resistance. A device of REN 1.0 has 25 Meg ohm of DC resistance.

Since the customer of a 'privacy LED' box presumably has several other
extension phones, such a box would need to have about 50Meg ohms of DC
resistance in its DC comparator (which is how I assume they detect an
off-hook extension), in order to have an REN of 0.5 (which seems to be
a reasonable design goal.)

Was this consultant right ? (Have the FCC 68 rules changed recently?)
If so, does anyone know if commercial units have such high resistance?

It's moderately challenging, I'd assume.


Regards, 

Jon Sreekanth

Assabet Valley Microsystems			Fax and PC products
346 Lincoln St #722, Marlboro, MA 01752		508-562-0722
jon_sree@world.std.com