Beacon Transmission Characteristics

Cospas-Sarsat 406 MHz distress beacons are provided in models which transmit either a "short" distress message or a "long" distress message as indicated below. 406 MHz beacon messages are comprised of:

a message preamble which is the combination of the 160 ms of unmodulated carrier, the bit synchronization pattern and the frame synchronization pattern;
various other data fields which provide a unique beacon identification and, depending upon the protocol used, other information that would be useful to Search and Rescue Authorities.

Note that additional information describing the contents of the message fields is provided by clicking on the appropriate section of the message format diagrams below.

Fields of the Short Message Format

	Bit Synch	Frame Synch	First Protected Data Field				BCH-1	Non-Protected Data Field
Unmodulated Carrier (160ms)	Bit Synch Pattern	Frame Synch Pattern	Format Flag	Protocol Flag	Country Code	Identification	21-BIT BCH Code	Emergency Code or National Use
	Bits 1 - 15	Bits 16 - 24	Bit 25	Bit 26	Bits 27 - 36	Bits 37 - 85	Bits 86 - 106	Bits 107 - 112
	15 Bits	9 Bits	1 Bit	1 Bit	10 Bits	49 Bits	21 Bits	6 Bits

Beacon Transmission Characteristics

Fields of the Short Message Format

Fields of the Long Message Format