Deferred Revenue

3 Months Ended

Mar. 31, 2019

Deferred Revenue Disclosure [Abstract]

Deferred Revenue

Note 12. Deferred Revenue

Deferred revenue, consisting of individually immaterial amounts for extended warranty, enhanced maintenance and advanced payments on non-recurring engineering services contracts, represents contracted revenue that has not yet been recognized.

The following table presents the changes in deferred revenue for the periods presented (in thousands):

	Three Months Ended March 31,
	2019			2018
Balance at beginning of period	$	834		$	1,215
Deferral of revenue		236			13
Recognition of deferred revenue		(69	)		(486	)
Balance at end of period	$	1,001		$	742