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:

* 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-ater-8 is the 8 kbit/s submultiplexing counterpart to itt-ater-16,
  corresponding to PCM circuit type B on TCSM2.

* 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.