Revenue

The Company differentiates revenue and cost of revenue based on whether the source of revenue is attributable to products, rentals or services. Revenue and cost of revenue by source are as follows (in thousands):



	Three months ended March 31,
	2014		2013
Revenue:
Products	$	82,406	$	56,330
Rentals	13,923		15,740
Services	6,246		6,173
	$	102,575	$	78,243
Cost of revenue:
Products	$	47,732	$	34,516
Rentals	6,513		6,517
Services	2,715		2,737
Depreciation	1,934		1,843
	$	58,894	$	45,613