Segment information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 04, 2015 USD ($)	Jun. 28, 2014 USD ($)	Jul. 04, 2015 USD ($) Segment	Jun. 28, 2014 USD ($)
Segment information [Abstract]
Number of reportable segments | Segment			2
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	$ 10,346	$ 9,657	$ 30,619	$ 27,876
Operating income (loss)	261	213	1,217	1,119
Identifiable assets, excluding goodwill	32,431	24,033	32,431	24,033
Reportable Segments [Member] | Controls [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	9,820	9,063	29,000	26,199
Operating income (loss)	342	194	1,064	1,033
Identifiable assets, excluding goodwill	24,033	21,907	24,033	21,907
Reportable Segments [Member] | Capacitors [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	526	594	1,619	1,677
Operating income (loss)	5	108	121	252
Identifiable assets, excluding goodwill	1,248	1,462	1,248	1,462
Intersegment Eliminations [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	0	3	3	5
Intersegment Eliminations [Member] | Controls [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	0	0	0	0
Intersegment Eliminations [Member] | Capacitors [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	0	3	3	5
Corporate [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Sales to external customers	0	0	0	0
Operating income (loss)	(86)	(89)	32	(166)
Identifiable assets, excluding goodwill	$ 7,150	$ 664	$ 7,150	$ 664