18.

Revenues

The following table represents a disaggregation of revenue from contracts with customers. Revenue originating from the following geographic areas for the years ended

December 31, 2019

and

2018

consist of:

	Year Ended December 31, 2019
	(in thousands)
	United States		United Kingdom		Germany		Rest of the world		Total
Instruments, equipment, software and accessories	$	78,196	$	10,607	$	13,359	$	8,058	$	110,220
Service, maintenance and warranty contracts		4,742		819		313		82		5,956
Total revenues	$	82,938	$	11,426	$	13,672	$	8,140	$	116,176

	Year Ended December 31, 2018
	(in thousands)
	United States		United Kingdom		Germany		Rest of the world		Total
Instruments, equipment, software and accessories	$	79,614	$	13,690	$	13,193	$	8,571	$	115,068
Service, maintenance and warranty contracts		4,438		832		366		70		5,706
Total revenues	$	84,052	$	14,522	$	13,559	$	8,641	$	120,774

Deferred revenue

The Company had approximately

$3.9

million and

$3.8

million in deferred revenue from service contracts and advance payments as of

December 31, 2019

and

2018,

respectively

. Changes in deferred revenue from service contracts and advance payments from customers during the period were as follows:

	Year Ended December 31, 2019
	(in thousands)
	Service Contracts			Customer Advances			Total
Balance, beginning of period	$	1,659		$	2,161		$	3,820
Deferral of revenue		2,152			1,095			3,247
Recognition of deferred revenue		(2,233	)		(894	)		(3,127	)
Effect of foreign currency translation		9			-			9
Balance, end of period	$	1,587		$	2,362		$	3,949

	Year Ended December 31, 2018
	(in thousands)
	Service Contracts			Customer Advances			Total
Balance, beginning of period	$	505		$	-		$	505
Addition due to business combination		848			2,128			2,976
Deferral of revenue		4,305			1,210			5,515
Recognition of deferred revenue		(3,984	)		(1,177	)		(5,161	)
Effect of foreign currency translation		(15	)		-			(15	)
Balance, end of period	$	1,659		$	2,161		$	3,820

Allowance for Doubtful Accounts

Allowance for doubtful accounts is based on the Company’s assessment of the collectability of customer accounts. A rollforward of allowance for doubtful accounts is as follows:

	Year Ended December 31,
	2019			2018
	(in thousands)
Balance, beginning of period	$	332		$	193
Addition due to business combination		-			103
Bad debt expense		288			25
Charge-offs and other recoveries		(293	)		12
Effect of foreign currency translation		(2	)		(1	)
Balance, end of period	$	325		$	332

Concentrations

customer accounted for more than

10%

of the revenues for the years ended

December 31, 2019,

and

2018.

December

31,

2019

and

2018,

customer accounted for more than

10%

of net accounts receivable.