Download Last Update: Aug 23, 1997

There is a 6 tone system (MK6) using ITA2 and a 12 tone
system (also MK6) using ASCII/ITA5 but the 6 tone system
is the more common. The 6 tone system is used mainly by
the British Gov., Australian Gov. stations and Chilean
Military. The 12 tone system is used mainly by the
British Gov.
Both of the above systems normally run at 20bd but a
40bd, double speed variant, known as PICCOLO MK10 has
been reported in use by British Gov. PICCOLO MK10 uses
6 tones, a special alphabet and different standby
tones. Both 20bd systems can still be found on the air
and the modern MK6 unit is manufactured by RACAL. The
40bd system is rarely found at this time. Reference the
Klingenfuss RadioTeletype Code Manual 13th Edition for
the tone pairs and PICCOLO MK6 alphabet.
For tuning purposes on a 6 tone PICCOLO MK6 signal,
zero between tones 3 and 4, on a 12 tone PICCOLO signal
zero between tones 6 and 7. A PICCOLO signal only has a
20Hz shift between tones so precise tuning is important
and the ability to magnify a signal is a great feature.
Inexact tuning will induce translation errors.
COQUELET
COQUELET Mk I is an asynchronous 13 tone ITA2 system
used by French (possibly abandoned) and Belgian mil./
police. COQUELET Mk II is a synchronous 8 tone ITA2
system used by Algerian Diplo and Customs. COQUELET
Mk I is also referred to as COQ13. COQUELET Mk II is
also referred to as COQ8 and can use a fourth shift
Arabic/Latin keyboard.
Also note that users of COQ8 seem to be using a hybrid
COQ8/COQ13 system (possible COQUELET Mk III?). It is
probable that this is COQ-82 or COQUELET-8 v2, a
synchronous scrambled system (mentioned as being
available on Wavecoms W41PC/W4100DSP) used on the
Algerian Diplo links. This system is capable of recognizing either Latin or Arabic keyboards and can switch
accordingly. The system has a distinctive 13.3bd preamble with a row of 'j's. This system is probably being
phased out.
COQ13 translates each 5 unit ITA-2 character into a
sequence of 2 tones out of total of 12. A 13th tone
represents the idle condition. The system takes each
character and breaks it into a 3 bit piece and a 2 bit
piece. The first 3 bits of the character are sent as 1
out of 8 possible tones (1-8) and the second 2 bits are
sent as 1 out of 4 possible tones (10-13). The idle
tone, tone 9, is heard only during the idle or standby
condition. Each tone is 75 ms in length or one character
is 150 ms long giving the system a baud rate of 13.5.
COQ8 directly translates each character into a set of
2 tones from a total set of 8 tones. The idle condition
used by this system is made up of tones 1 and 8 sent
alternating. Each tone has a duration of 37.5 ms or
75 ms, giving an effective baud rate of 26.67 or 13.3.
Baud rates of 53.3 have also been monitored.
For tuning purposes on a 13 tone Coquelet signal, zero
on tone 9 during standby or between tone 8 and 10. On
an 8 tone Coquelet signal zero between tones 1 and 8,
these tones alternating is the idle condition. In
general, a Coquelet signal only has a 30Hz shift
between tones so exact tuning is important and the
ability to magnify a signal is a great feature.