292 THE BELL SYSTEM TECHNICAL JOTRXAL, JANUARY 1957 



depends upon the probabilit}' of the primary sources at the terminal 

 stations faihng simultaneously. 



ACKNOWLEDGMENTS . 



The authors wish to express their thanks to man}' of their colleagues 

 in the Post Office and Standard Telephones and Cables, Ltd., who have 

 contributed to the developments described in the paper. The permission 

 of the Engineer-in-Chief of the Post Office, and of Standard Telephones 

 and Cables, Ltd., to make use of the information contained in the paper 

 is also gratefull}^ acknowledged. The equipments for the Clarenville- 

 S3'dnej^ Mines link were manufactured b}' Standard Telephones and 

 Cables, Ltd., at North Woolwich, London. 



