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Piccolo
Mulitple Frequency-Shift Keying

Piccolo was a telegraphy system, used by the Diplomatic Wireless Service (DWS) in the UK, for sending and receiving digital data in ITA-2 (5-bit baudot) or ITA-5 (7-bit ASCII) format over narrow-band Short Wave (SW) radio channels, using Multiple Frequency-Shift Keying (MFSK) modulation. Various implementations of Piccolo have emerged over the years:

Piccolo I
The first generation Piccolo dates back to 1962. It consists of 32 distincive tones, one for each character of the ITA-2 alphabet, 10 Hz apart. It was intended for low-speed teleprinter signals over HF radio links at 50 or 75 baud. Also known as Muli-Level FSK (MFSK) or Polytone.

#ToneCode  
0460 Hz00000  
1470 Hz00001  
2480 Hz00010  
3490 Hz00011  
4500 Hz00100  
5510 Hz00101  
6520 Hz00110  
7530 Hz00111  
8540 Hz01000  
9550 Hz01001  
10560 Hz01010  
11570 Hz01011  
12580 Hz01100  
13590 Hz01101  
14600 Hz01110  
15610 Hz01111  
16620 Hz10000  
17630 Hz10001  
18640 Hz10010  
19650 Hz10011  
20660 Hz10100  
21670 Hz10101  
22680 Hz10110  
23690 Hz10111  
24700 Hz11000  
25710 Hz11001  
26720 Hz11010  
27730 Hz11011  
28740 Hz11100  
29750 Hz11101  
30760 Hz11110  
31770 Hz11111  
Piccolo II
The Piccolo II standard supports the same 10 characters per second, but needs only 6 distinctive audio tones, each 20 Hz apart, starting at 460 Hz. Two such tones, each 50 ms long, are sent in quick succession in order to achieve ITA-2 compatibility. This way, 36 codes can be made.

 
ITA2
#Tone
A460 Hz
B480 Hz
C500 Hz
D520 Hz
E540 Hz
F560 Hz

The matrix above shows the 36 characters (6 x 6) that can be generated by creating tone pair from the table below, and how these characters are translated to the ITA2 standard. As the ITA2 standard supports only 32 characters (25), 4 characters are unused. These tone pairs (DD, DE, ED and EE), shown here in grey, are used for synchronisation (SYNC) and Multiple Ident (MI). Tone pair DD is not used at all. The table above gives the Piccolo II tones for the ITA-2 standard.

ITA5
A similar approach is used when using the Piccolo II standard for sending ITA-5 compatible data (7-bit ASCII). In this case, 12 distinct tones are used, allowing a maximum of 144 characters to be defined (12 x 12). At present, the translation matrix to 7-bit ASCII is not available.

 
ITA2
#Tone
A400 Hz
B420 Hz
C440 Hz
D460 Hz
E480 Hz
F500 Hz
G520 Hz
H540 Hz
I560 Hz
J580 Hz
K600 Hz
L620 Hz
Piccolo III
The Piccolo III standard follows the same scheme for ITA2 data as the Piccolo II standard shown above, but uses higher frequency audio tones, starting at 1900 Hz, each 40 Hz apart. These scheme is used, for example, by the FRM-4750 and the FRM-4780 Data Radio Stations.

 
ITA2
#Tone
A1900 Hz
B1940 Hz
C1980 Hz
D2020 Hz
E2060 Hz
F2100 Hz


Piccolo IV
The specification of the Piccolo IV standard is currently unknown. If you have more information, please contact us.


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Crypto Museum. Created: Thursday 16 April 2015. Last changed: Sunday, 29 December 2024 - 10:05 CET.
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