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(11) Concentrations of Credit Risk, Significant Customers and Geographic Information (Tables)
12 Months Ended
Dec. 26, 2020
Accounting Policies [Abstract]  
Significant custmers as a percentage
   Percent of Total Revenues
       
Significant Customer   2020    2019 
A   36%   43%
B   21%   14%
C   16%   13%
Revenue derived from following countries
   Percent of Total Revenues
       
Country   2020    2019 
United States of America   23%   25%
Germany   36%   44%
Other   41%   31%