CONSOLIDATED FINANCIAL STATEMENT COMPONENTS

Depreciation, Amortization and Accretion

Depreciation, amortization and accretion expenses consisted of the following for the periods stated:



	For the Three Months Ended June 30,						For the Six Months Ended June 30,
(Dollars in thousands)	2018			2017			2018			2017
Depreciation
Leasehold improvements	$	67		$	75		$	135		$	125
Asset retirement costs	(76		)	(97		)	(152		)	(195		)
Paging and computer equipment	1,815			2,028			3,670			4,087
Furniture, fixtures and vehicles	103			76			209			141
Total depreciation	1,909			2,082			3,862			4,158
Amortization	625			629			1,250			1,636
Accretion	135			140			270			280
Total depreciation, amortization and accretion expense	$	2,669		$	2,851		$	5,382		$	6,074

Accounts Receivable, Net

Accounts receivable was recorded net of an allowance of $1.5 million and $1.1 million at June 30, 2018 and December 31, 2017, respectively. Accounts receivable, net includes $10.1 million and $7.3 million of unbilled receivables at June 30, 2018 and December 31, 2017, respectively. Unbilled receivables are defined as the Company's right to consideration in exchange for goods or services that we have transferred to the customer but have not yet billed for, generally as a result of contractual billing terms. The increase in unbilled receivables was primarily due to the adoption of ASC 606 and the acceleration of license revenue for the six months ended June 30, 2018 .

Property and Equipment, Net

Property and equipment, net consisted of the following as of the date stated:



(Dollars in thousands)	Useful Life (In Years)	June 30, 2018			December 31, 2017
Leasehold improvements	shorter of useful life or lease term	$	4,135		$	4,107
Asset retirement costs	1-5	3,267			3,228
Paging and computer equipment	1-5	101,526			103,520
Furniture, fixtures and vehicles	3-5	5,345			4,545
Total property and equipment		114,273			115,400
Accumulated depreciation		(101,238		)	(102,001		)
Total property and equipment, net		$	13,035		$	13,399

Other Current Liabilities

Other current liabilities consisted of the following as of the date stated:



(Dollars in thousands)	June 30, 2018		December 31, 2017
Accrued network costs, asset retirement obligations and other	$	2,496	$	2,173
Accrued outside services	1,514		2,437
Total other current liabilities	$	4,010	$	4,610

Other Non-Current Liabilities

Other non-current liabilities consisted of the following as of the date stated:



(Dollars in thousands)	June 30, 2018		December 31, 2017
Asset retirement obligations	$	7,351	$	7,174
Other	1,042		901
Total other non-current liabilities	$	8,393	$	8,075