3. Changes in Accounting Policies: Schedule of impacts of accounting changes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2017
Cash and cash equivalents	$ 5,154		$ 5,154		$ 5,276
Restricted cash	405		405		312
Contract revenue in excess of billings	4,657		4,657		2,763
Inventories, net	4,258		4,258		3,973
Total assets	28,749		28,749		25,030
Billings in excess of contract revenue	9,229		9,229		7,117
Total liabilities	24,107		24,107		21,805
Accumulated deficit	(45,867)		(45,867)		(47,208)
Total stockholders' equity	4,642		4,642		3,225
Total liabilities and stockholders' equity	28,749		28,749		$ 25,030
Sales	8,872	$ 6,744	16,453	$ 14,787
Cost of sales	(5,654)	(4,479)	(10,556)	(9,848)
Selling, general and administrative	(1,685)	(1,517)	(3,431)	(3,123)
Income tax provision	(20)	(3)	(31)	(18)
Net income	619	$ (171)	658	14
Changes in operating assets and liabilities:
Decrease (increase) in inventories			(1,367)	323
Increase in contract revenue in excess of billings			(1,140)	(644)
Increase in billings in excess of contract revenue			2,964	809
Net cash provided by operating activities			137	(1,297)
Net cash used in investing activities			(56)	(86)
Net cash used in financing activities			(110)	$ (105)
As reported
Cash and cash equivalents	5,154		5,154
Restricted cash	405		405
Contract revenue in excess of billings	4,657		4,657
Inventories, net	4,258		4,258
Others	14,275		14,275
Total assets	28,749		28,749
Billings in excess of contract revenue	9,229		9,229
Others	14,878		14,878
Total liabilities	24,107		24,107
Accumulated deficit	(45,867)		(45,867)
Others	50,509		50,509
Total stockholders' equity	4,642		4,642
Total liabilities and stockholders' equity	28,749		28,749
Sales	8,872		16,453
Cost of sales	(5,654)		(10,556)
Selling, general and administrative	(1,685)		(3,431)
Income tax provision	(20)		(31)
Others	(894)		(1,777)
Net income	619		658
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Other			125
Changes in operating assets and liabilities:
Decrease (increase) in inventories			(1,367)
Increase in contract revenue in excess of billings			(1,140)
Increase in billings in excess of contract revenue			2,964
Increase in contract liabilities			(1,103)
Net cash provided by operating activities			137
Net cash used in investing activities			(56)
Net cash used in financing activities			(110)
Scenario, Adjustment
Cash and cash equivalents	0		0
Restricted cash	0		0
Contract revenue in excess of billings	(978)		(978)
Inventories, net	1,754		1,754
Others	0		0
Total assets	776		776
Billings in excess of contract revenue	1,938		1,938
Others	0		0
Total liabilities	1,938		1,938
Accumulated deficit	(1,162)		(1,162)
Others	0		0
Total stockholders' equity	(1,162)		(1,162)
Total liabilities and stockholders' equity	776		776
Sales	(876)		(1,310)
Cost of sales	630		831
Selling, general and administrative	0		0
Income tax provision	0		0
Others	0		0
Net income	(246)		(479)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Other			0
Changes in operating assets and liabilities:
Decrease (increase) in inventories			(831)
Increase in contract revenue in excess of billings			978
Increase in billings in excess of contract revenue			332
Increase in contract liabilities			0
Net cash provided by operating activities			0
Net cash used in investing activities			0
Net cash used in financing activities			0
Balances without adoption of Topic 606
Cash and cash equivalents	5,154		5,154
Restricted cash	405		405
Contract revenue in excess of billings	3,679		3,679
Inventories, net	6,012		6,012
Others	14,275		14,275
Total assets	29,525		29,525
Billings in excess of contract revenue	11,167		11,167
Others	14,878		14,878
Total liabilities	26,045		26,045
Accumulated deficit	(47,029)		(47,029)
Others	50,509		50,509
Total stockholders' equity	3,480		3,480
Total liabilities and stockholders' equity	29,525		29,525
Sales	7,996		15,143
Cost of sales	(5,024)		(9,725)
Selling, general and administrative	(1,685)		(3,431)
Income tax provision	(20)		(31)
Others	(894)		(1,777)
Net income	$ 373		179
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Other			125
Changes in operating assets and liabilities:
Decrease (increase) in inventories			(2,198)
Increase in contract revenue in excess of billings			(162)
Increase in billings in excess of contract revenue			3,296
Increase in contract liabilities			(1,103)
Net cash provided by operating activities			137
Net cash used in investing activities			(56)
Net cash used in financing activities			$ (110)