--- a/README	Thu Aug 29 19:02:02 2024 +0000
+++ b/README	Thu Aug 29 19:42:22 2024 +0000
@@ -1,12 +1,26 @@
-The test programs in this Hg repository are being developed ahead of the needed
-hardware.  These programs are intended to run on a machine equipped with an
-icE1usb adapter (more specifically, one that is capable of bringing up both E1
-interfaces on that adapter) and running osmo-e1d, with the two E1 circuits out
-of icE1usb connected to A and Ater interfaces of Nokia TCSM2 bank-of-TRAUs
-apparatus.
+The test programs in this Hg repository are intended to run on a Raspberry Pi 5
+driving an icE1usb adapter, which is in turn connected to Nokia TCSM2
+bank-of-TRAUs apparatus via PCM and Ater interfaces.  Both E1 ports on icE1usb
+have to be used (one E1 circuit for PCM, the other for Ater), and RPi5 has to
+be used as the driving host because it is one of the few host machine types
+that can successfully operate icE1usb with both E1 interfaces.
+
+The test programs in the present suite use Osmocom libraries and work through
+osmo-e1d, opening individual E1 timeslots as needed.  The test programs are:
 
-As of this writing, the additional TCSM2 components that bring out the E1
-circuits have not been procured yet; the needed icE1usb device is likewise
-still on order.  In the meantime, test programs that are ultimately intended
-for exercising the TRAU are being developed in a virtual environment, using
-osmo-e1d with vpair interfaces.
+* itt-ater-16 operates on a single E1 ts on Ater and treats it as consisting of
+  four 16 kbit/s subslots, corresponding to PCM circuit type A on TCSM2.  Each
+  individual TRAU channel comes to life when TRAU-UL frames appear in the
+  corresponding subslot on Ater, thus itt-ater-16 can activate up to 4 TRAU
+  channels that share the same E1 ts.  For each channel it activates, our test
+  program can feed any desired UL frame stream to the TRAU, thereby facilitating
+  functional experimentation.
+
+* itt-pcm-one operates on a single E1 ts on A interface, aka PCM.  It can
+  display and record PCM output from the TRAU, and it can feed different PCM
+  byte patterns to the TRAU.
+
+* itt-pcm-br (PCM bridge) opens two different E1 timeslots on the PCM side of
+  the TRAU apparatus and bridges them together, forwarding all bytes from A to
+  B and from B to A.  This bridging function is needed in order to exercise TFO,
+  involving two TRAU channels in the TCSM2 bank-of-TRAUs apparatus.