This is an external keyer which generates a two-tone signal for transmission on the 2182 KHz distress frequency. It can be used with any transmitter made by Marconi Marine and would be plugged into the key input of the main or reserve transmitter.

The alarm signal consists of two sinusoidal audio-frequency tones, transmitted alternately. One tone has a frequency of 2200 Hz and the other a frequency of 1300 Hz. The duration of each tone is 250 ms.When operating, the two tone signal sounds similar to the alarm of a European ambulance. (ie  Dee-dah, dee-dah, dee-dah....etc). When generated by automatic means, the alarm signal shall be sent continuously for a period of at least 30 seconds but not exceeding one minute. If generated by other means, the signal shall be sent as continuously as is practicable over a period of approximately one minute.

It was made by M & G Electronics (outsource manufacturer) for Coastal Radio, a Marconi Marine Company.
The Mk II unit is presumed to be solid state.

Coast Alert II photo courtesy  Radio Officers.com web page

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Contributors and Credits:

1) Sandy Blaize  <ebjr37(at)charter.net>
2) http://www.radioofficers.com/galleries/fort-perch-museum/attachment/fpr-akd/
3) http://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.219-1-196607-W!!PDF-E.pdf
 

Oct 22/12