The CM startup sequence generated by the HTU-C is as follows:

1. 3 s of silence.

2. A pulse train is transmitted which encodes the data rate.  During pulse
   transmission the bitpump is operated at 80 kHz symbol clock and pulses are
   generated by turning the transmitter on and off for a set number of symbol
   periods (using the bitpump's general purpose timer 3).

   The pulse train consists of one 300 ms pulse followed by N 150 ms pulses and
   then one more 300 ms pulse.  Pulses are separated by 150 ms of silence.  The
   number of 150 ms pulses encodes the data rate as follows:

   0 =  160 kbps
   1 =  208 kbps
   2 =  320 kbps
   3 =  416 kbps
   4 =  392 kbps
   5 =  784 kbps
   6 = 1040 kbps
   7 = 1568 kbps
   8 = 2320 kbps

3. 100 ms of silence.

4. The bitpump clock is switched to the operational symbol rate and the
   standard HTU-C startup sequence begins.