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):



	Year ended December 31,
	2013		2012		2011
Revenue:
Products	$	282,639	$	224,777	$	181,417
Rentals	62,042		67,938		63,610
Services	26,384		20,113		13,758
	$	371,065	$	312,828	$	258,785
Cost of Revenue:
Products	$	180,800	$	135,367	$	115,875
Rentals	24,987		30,618		25,971
Services	9,916		8,051		4,997
Depreciation	7,835		7,173		6,122
	$	223,538	$	181,209	$	152,965