README: update explaining the difference to other approaches

Change-Id: Ie6afe8016c0168c2f0beee96d6c151c5b4cc5e81
---
M README
1 file changed, 17 insertions(+), 4 deletions(-)


git pull ssh://gerrit.osmocom.org:29418/osmo-e1-recorder refs/changes/33/30033/1

diff --git a/README b/README
index 149b547..1f7bc72 100644
--- a/README
+++ b/README
@@ -2,11 +2,24 @@
 ===================
 (C) 2016 by Harald Welte <laforge@gnumonks.org>
 
-The idea of this program is to be able to passively record E1/T1 based
-communications for purposes of data analysis.
+The idea of this program is to be able to build a "poor mans E1/T1
+recorder" purposes of data analysis, *without* any special
+equipment.
 
-Recording of a single E1 link always requires two E1 interface cards,
-one for each direction.
+This approach is more risky than a purely passive, hardware based
+approach as that of the Osmocom e1-tracer released at
+https://osmocom.org/projects/e1-t1-adapter/wiki/E1_tracer
+
+If you can, it is strongly recommended to use the purely passive,
+high-impedance tap approach of e1-tracer and not the poor-man's
+software proxy approach presented in osmo-e1-recorder.
+
+Setup
+-----
+
+To do so, two E1 cards are used as some kind of proxy for the E1
+communication.  Recording of a single E1 link always requires two E1
+interface cards, one for each direction.
 
 Recording can be performed either
 * passively, using a E1 Tap aapter

