Note 2 - Revenue (Details)	12 Months Ended
Dec. 31, 2019
Maintenance and Service
Products and services segment	Part sales typically range from $1 to $100. Maintenance and Service contract sales typically range from $3 to $200.
Audio-Visual Systems
Products and services segment	Sales of typical Audio-Visual Systems range from $200 to $2,000.

Description of the types of products and services from which the reportable segment derives its revenue.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8721-108599

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration