we have recently introduced several new wafersense ® products to further enhance our revenue growth prospects . the in-line particle sensor ( ips ) detects particles in gas and vacuum lines in semiconductor process equipment , and is particularly relevant for euv lithography tools where the ability to monitor particles in-line can significantly improve tool yield and productivity . the wafersense ® 300mm auto resistance sensor ( ars ) enables real-time resistance measurements of plating cell contacts in semiconductor electrochemical deposition ( ecd ) applications . the wafersense® auto vibration and leveling sensor ( avls3 ) with a thickness of 3.5mm can travel to most locations and tools within a semiconductor fabrication facility where a real semiconductor wafer travels . the avls3 collects and displays both vibration and leveling data simultaneously for fast equipment set-up , alignment and real-time equipment diagnostics . strong future sales growth is anticipated for the wafersense® family of products . 20 our backlog was $ 17.7 million at december 31 , 2019 , an increase from $ 14.4 million at september 30 , 2019 , and $ 13.6 million at december 31 , 2018. the order backlog at december 31 , 2019 and september 30 , 2019 includes a significant order for 3d mrs sensors from an existing oem customer that is scheduled for delivery in the next 18 months . we are forecasting sales of $ 15.0 to $ 16.5 million for the first quarter of 2020. we believe that demand in the smt and semiconductor capital equipment markets will continue to strengthen through 2020. however , a prolonged coronavirus epidemic or an increase in severity of the current outbreak could cause a slow-down in demand for smt and semiconductor capital equipment . we believe that anticipated sales growth of our 3d mrs-enabled products and wafersense sensors should increase our revenues and net income in the future . we believe that we have the resources required to attain our growth objectives , given our available cash and marketable securities balances totaling $ 26.3 million at december 31 , 2019. our ability to implement our strategy effectively is subject to numerous uncertainties and risks , including the risks identified in item 1 a of this annual report on form 10-k. revenues our revenues decreased by 8 % to $ 59.3 million in 2019 , from $ 64.7 million in 2018 , and increased by 21 % to $ 64.7 million in 2018 , from $ 53.3 million in 2017. the following table sets forth , for the years indicated , revenues by product line : replace_table_token_1_th revenues from sales of high precision 3 d and 2 d sensors decreased by $ 9.0 million or 42 % to $ 12.6 million in 2019 , from $ 21.5 million in 2018 , and increased by $ 4.5 million or 26 % to $ 21.5 million in 2018 , from $ 17.1 million in 2017. sales of 3 d mrs sensors decreased by $ 1.8 million or 23 % to $ 6.0 million in 2019 , from $ 7.9 million in 2018 , and increased by $ 3.5 million or 80 % to $ 7.9 million in 2018 , from $ 4.4 million in 2017. the revenue decrease in 2019 resulted from a reduction of purchases by oem customers for high precision 3d and 2d sensors due to weak demand in the global smt and semiconductor capital equipment markets . the revenue increase in 2018 primarily resulted from higher sales of 3d mrs-enabled sensors , reflecting higher adoption rates by our oem customers for these products . sales of 3d mrs-enabled sensors started to rebound in early 2020 , reflecting improving conditions in the market for semiconductor capital equipment . we believe sales of older high precision 2d sensors will also rebound , but recovery may not happen until later in 2020. we believe sales of our 3d mrs enabled sensors , including our next generation ultra-high resolution 3d nanoresolution mrs sensor , will continue to grow in the future , and will represent an increasing percentage of our total high precision 3d and 2d sensor sales . sales of high precision 3 d and 2 d sensors are prone to significant fluctuations , both sequentially and on a year-over-year basis , due to variations in market demand . sales of high precision 3 d and 2 d sensors are dependent on the success of oems and system integrators selling products that incorporate our sensors . revenues from sales of inspection and metrology systems increased by $ 3.1 million or 11 % to $ 32.7 million in 2019 , from $ 29.6 million in 2018 , and increased by $ 4.4 million or 17 % to $ 29.6 million in 2018 , from $ 25.2 million in 2017 . revenues from sales of inspection and metrology systems increased in 2019 and 2018 because higher sales of sq3000 multi-function inspection and measurement systems and 2d mx600 systems for memory module inspection were able to offset lower sales of legacy products . sales of sq3000 multi-function systems increased by $ 4.6 million or 36 % to $ 17.5 million in 2019 , from $ 12.9 million in 2018 , and increased by $ 3.4 million or 36 % to $ 12.9 million in 2018 , from $ 9.5 million in 2017. sales of sq3000 multi-function systems increased in 2019 , despite a global decline in spending for smt and semiconductor capital equipment , because of the competitive advantages offered by our sq3000 multi-function system products , and because many companies are transitioning from 2 d aoi to 3 d aoi to meet the increasingly demanding product inspection and metrology requirements in the smt and semiconductor markets . story_separator_special_tag we maintain allowances for doubtful accounts for estimated losses resulting from the inability of our customers to make required payments . in making the determination of the appropriate allowance for doubtful accounts , we consider specific accounts , historical write-offs , changes in customer relationships and credit worthiness and concentrations of credit risk . specific accounts and trade notes receivable are written-off once a determination is made that the account is uncollectible . if the financial condition of our customers were to deteriorate , resulting in an impairment of their ability to make payments , additional allowances may be required . the allowance for doubtful accounts and trade notes was $ 322,000 at december 31 , 2019 and $ 314,000 at december 31 , 2018. allowance for warranty expenses . we provide for the estimated cost of product warranties at the time revenue is recognized . while we engage in extensive product quality programs and processes , including actively monitoring and evaluating the quality of components provided by suppliers , warranty obligations do arise . these obligations are affected by product failure rates , the costs of materials used and service delivery expenses incurred in correcting a product failure . if actual product failure rates and material or service delivery costs differ from our estimates , revisions to the estimated warranty liability are required and could be material . the allowance for warranties was $ 798,000 at december 31 , 2019 and $ 789,000 at december 31 , 2018. inventory write downs . we write down inventory for estimated obsolescence or lack of marketability equal to the difference between the cost of inventory and the estimated market value based upon assumptions about future demand and market conditions . we formulate our assumptions regarding future demand and market conditions based on order trends and input from customers regarding their future requirements . if actual market conditions are less favorable than those projected , or if in the future we decide to discontinue sales and marketing of any of our products , additional inventory write-downs may be required . excess and obsolete inventories were written down by $ 649,000 at december 31 , 2019 and $ 718,000 at december 31 , 2018. valuation of intangible and long-lived assets . we evaluate the carrying value of goodwill annually on december 31 , and more frequently if management believes indicators of impairment exist . we assess the impairment of identifiable intangible assets , long lived assets and related goodwill whenever events or changes in circumstances indicate the carrying value may not be recoverable . factors we consider important , which could trigger an impairment review and that we consider when performing our annual goodwill impairment assessment , include the following : significant under-performance relative to expected historical or projected future operating results . significant changes in the manner of our use of the acquired assets or the strategy for our overall business . significant negative industry or economic trends . significant decline in the price of our common stock for a sustained period , and the size of our market capitalization relative to our net book value . for intangible and long-lived assets , if the carrying value exceeds the undiscounted cash flows from such asset . for goodwill , if the carrying value of our net assets ( net book value ) exceeds fair value . 26 when we determine that the carrying value of intangibles , long-lived assets and related goodwill may not be recoverable based upon the existence of one or more of the above indicators of impairment , we measure any potential impairment based on a projected discounted cash flow method using a discount rate that we believe is commensurate with the risk inherent in our current business model . we utilize the income approach to estimate our fair value . the income approach is a valuation technique under which we estimate future cash flows using financial forecasts . future estimated cash flows are discounted to their present value to calculate fair value . when determining fair value , we also give consideration to the control premium in excess of our current market capitalization that might be obtained from a third party acquirer . these assumptions require significant judgment and actual results may differ from assumed or estimated amounts . at december 31 , 2019 , we had goodwill of $ 1.4 million . our recent analysis performed as of december 31 , 2019 indicates that our goodwill is not impaired . however , our conclusion could change in the future , if our assumptions about future economic conditions , revenue growth or profitability change . any resulting impairment charge could have a material effect on our financial position and results of operations in the future . income taxes . significant judgment is required in determining worldwide income tax expense based upon tax laws in the various jurisdictions in which we operate . we have established reserves for uncertain tax positions by applying the “ more likely than not ” threshold ( i.e . , a likelihood of occurrence greater than fifty percent ) . the recognition threshold is met when an entity concludes that a tax position , based solely on its technical merits , is more likely than not to be sustained upon examination by the relevant taxing authority . those tax positions failing to qualify for initial recognition are recognized in the first interim period in which they meet the more likely than not standard , or are resolved through negotiation or litigation with the taxing authority , or upon expiration of the statute of limitations . de-recognition of a tax position that was previously recognized occurs when an entity subsequently determines that a tax position no longer meets the more likely than not threshold of being sustained . all tax positions are analyzed periodically and adjustments are made as events warrant modification , such as the completion of audits or the expiration of statutes of limitations

liquidity and capital resources our cash and cash equivalents decreased by $ 3.4 million in 2019. cash provided by operating activities of $ 2.1 million and proceeds of $ 7.8 million from maturities of marketable securities were more than offset by purchases of marketable securities totaling $ 12.0 million and purchases of fixed assets and payment of capitalized patent costs totaling $ 1.5 million . our cash and cash equivalents fluctuate in part because of sales and maturities of marketable securities and investment of cash balances in marketable securities , and from other sources of cash . accordingly , we believe the combined balances of cash and marketable securities provide a more reliable indication of our available liquidity than cash balances alone . combined balances of cash and marketable securities increased by $ 1.0 million to $ 26.3 million as of december 31 , 2019 , from $ 25.3 million as of december 31 , 2018. operating activities provided $ 2.1 million of cash in 2019 . the amount of cash provided by operations was favorably impacted by our net income of $ 774,000. net income was affected by non-cash expenses totaling $ 5.2 million for depreciation and amortization , non-cash operating lease expense , provision for doubtful accounts , deferred taxes , non-cash losses from foreign currency transactions , share-based compensation costs , and various non-cash gains and losses . changes in operating assets and liabilities providing cash included a decrease in prepaid expenses and other assets of $ 539,000 . changes in operating assets and liabilities using cash included an increase in accounts and trade notes receivable of $ 1.2 million , an increase in inventories of $ 439,000 , a decrease in accounts payable of $ 1.5 million , a decrease in accrued expenses of $ 856,000 and a decrease in operating lease liabilities of $ 308,000. prepaid expenses and other assets mainly decreased because deposits previously paid to a key supplier of materials were used to purchase inventories . accounts and trade notes receivable increased due to slower collection of accounts receivable .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```liquidity and capital resources our cash and cash equivalents decreased by $ 3.4 million in 2019. cash provided by operating activities of $ 2.1 million and proceeds of $ 7.8 million from maturities of marketable securities were more than offset by purchases of marketable securities totaling $ 12.0 million and purchases of fixed assets and payment of capitalized patent costs totaling $ 1.5 million . our cash and cash equivalents fluctuate in part because of sales and maturities of marketable securities and investment of cash balances in marketable securities , and from other sources of cash . accordingly , we believe the combined balances of cash and marketable securities provide a more reliable indication of our available liquidity than cash balances alone . combined balances of cash and marketable securities increased by $ 1.0 million to $ 26.3 million as of december 31 , 2019 , from $ 25.3 million as of december 31 , 2018. operating activities provided $ 2.1 million of cash in 2019 . the amount of cash provided by operations was favorably impacted by our net income of $ 774,000. net income was affected by non-cash expenses totaling $ 5.2 million for depreciation and amortization , non-cash operating lease expense , provision for doubtful accounts , deferred taxes , non-cash losses from foreign currency transactions , share-based compensation costs , and various non-cash gains and losses . changes in operating assets and liabilities providing cash included a decrease in prepaid expenses and other assets of $ 539,000 . changes in operating assets and liabilities using cash included an increase in accounts and trade notes receivable of $ 1.2 million , an increase in inventories of $ 439,000 , a decrease in accounts payable of $ 1.5 million , a decrease in accrued expenses of $ 856,000 and a decrease in operating lease liabilities of $ 308,000. prepaid expenses and other assets mainly decreased because deposits previously paid to a key supplier of materials were used to purchase inventories . accounts and trade notes receivable increased due to slower collection of accounts receivable .
```    
 Suspicious Activity Report : we have recently introduced several new wafersense ® products to further enhance our revenue growth prospects . the in-line particle sensor ( ips ) detects particles in gas and vacuum lines in semiconductor process equipment , and is particularly relevant for euv lithography tools where the ability to monitor particles in-line can significantly improve tool yield and productivity . the wafersense ® 300mm auto resistance sensor ( ars ) enables real-time resistance measurements of plating cell contacts in semiconductor electrochemical deposition ( ecd ) applications . the wafersense® auto vibration and leveling sensor ( avls3 ) with a thickness of 3.5mm can travel to most locations and tools within a semiconductor fabrication facility where a real semiconductor wafer travels . the avls3 collects and displays both vibration and leveling data simultaneously for fast equipment set-up , alignment and real-time equipment diagnostics . strong future sales growth is anticipated for the wafersense® family of products . 20 our backlog was $ 17.7 million at december 31 , 2019 , an increase from $ 14.4 million at september 30 , 2019 , and $ 13.6 million at december 31 , 2018. the order backlog at december 31 , 2019 and september 30 , 2019 includes a significant order for 3d mrs sensors from an existing oem customer that is scheduled for delivery in the next 18 months . we are forecasting sales of $ 15.0 to $ 16.5 million for the first quarter of 2020. we believe that demand in the smt and semiconductor capital equipment markets will continue to strengthen through 2020. however , a prolonged coronavirus epidemic or an increase in severity of the current outbreak could cause a slow-down in demand for smt and semiconductor capital equipment . we believe that anticipated sales growth of our 3d mrs-enabled products and wafersense sensors should increase our revenues and net income in the future . we believe that we have the resources required to attain our growth objectives , given our available cash and marketable securities balances totaling $ 26.3 million at december 31 , 2019. our ability to implement our strategy effectively is subject to numerous uncertainties and risks , including the risks identified in item 1 a of this annual report on form 10-k. revenues our revenues decreased by 8 % to $ 59.3 million in 2019 , from $ 64.7 million in 2018 , and increased by 21 % to $ 64.7 million in 2018 , from $ 53.3 million in 2017. the following table sets forth , for the years indicated , revenues by product line : replace_table_token_1_th revenues from sales of high precision 3 d and 2 d sensors decreased by $ 9.0 million or 42 % to $ 12.6 million in 2019 , from $ 21.5 million in 2018 , and increased by $ 4.5 million or 26 % to $ 21.5 million in 2018 , from $ 17.1 million in 2017. sales of 3 d mrs sensors decreased by $ 1.8 million or 23 % to $ 6.0 million in 2019 , from $ 7.9 million in 2018 , and increased by $ 3.5 million or 80 % to $ 7.9 million in 2018 , from $ 4.4 million in 2017. the revenue decrease in 2019 resulted from a reduction of purchases by oem customers for high precision 3d and 2d sensors due to weak demand in the global smt and semiconductor capital equipment markets . the revenue increase in 2018 primarily resulted from higher sales of 3d mrs-enabled sensors , reflecting higher adoption rates by our oem customers for these products . sales of 3d mrs-enabled sensors started to rebound in early 2020 , reflecting improving conditions in the market for semiconductor capital equipment . we believe sales of older high precision 2d sensors will also rebound , but recovery may not happen until later in 2020. we believe sales of our 3d mrs enabled sensors , including our next generation ultra-high resolution 3d nanoresolution mrs sensor , will continue to grow in the future , and will represent an increasing percentage of our total high precision 3d and 2d sensor sales . sales of high precision 3 d and 2 d sensors are prone to significant fluctuations , both sequentially and on a year-over-year basis , due to variations in market demand . sales of high precision 3 d and 2 d sensors are dependent on the success of oems and system integrators selling products that incorporate our sensors . revenues from sales of inspection and metrology systems increased by $ 3.1 million or 11 % to $ 32.7 million in 2019 , from $ 29.6 million in 2018 , and increased by $ 4.4 million or 17 % to $ 29.6 million in 2018 , from $ 25.2 million in 2017 . revenues from sales of inspection and metrology systems increased in 2019 and 2018 because higher sales of sq3000 multi-function inspection and measurement systems and 2d mx600 systems for memory module inspection were able to offset lower sales of legacy products . sales of sq3000 multi-function systems increased by $ 4.6 million or 36 % to $ 17.5 million in 2019 , from $ 12.9 million in 2018 , and increased by $ 3.4 million or 36 % to $ 12.9 million in 2018 , from $ 9.5 million in 2017. sales of sq3000 multi-function systems increased in 2019 , despite a global decline in spending for smt and semiconductor capital equipment , because of the competitive advantages offered by our sq3000 multi-function system products , and because many companies are transitioning from 2 d aoi to 3 d aoi to meet the increasingly demanding product inspection and metrology requirements in the smt and semiconductor markets . story_separator_special_tag we maintain allowances for doubtful accounts for estimated losses resulting from the inability of our customers to make required payments . in making the determination of the appropriate allowance for doubtful accounts , we consider specific accounts , historical write-offs , changes in customer relationships and credit worthiness and concentrations of credit risk . specific accounts and trade notes receivable are written-off once a determination is made that the account is uncollectible . if the financial condition of our customers were to deteriorate , resulting in an impairment of their ability to make payments , additional allowances may be required . the allowance for doubtful accounts and trade notes was $ 322,000 at december 31 , 2019 and $ 314,000 at december 31 , 2018. allowance for warranty expenses . we provide for the estimated cost of product warranties at the time revenue is recognized . while we engage in extensive product quality programs and processes , including actively monitoring and evaluating the quality of components provided by suppliers , warranty obligations do arise . these obligations are affected by product failure rates , the costs of materials used and service delivery expenses incurred in correcting a product failure . if actual product failure rates and material or service delivery costs differ from our estimates , revisions to the estimated warranty liability are required and could be material . the allowance for warranties was $ 798,000 at december 31 , 2019 and $ 789,000 at december 31 , 2018. inventory write downs . we write down inventory for estimated obsolescence or lack of marketability equal to the difference between the cost of inventory and the estimated market value based upon assumptions about future demand and market conditions . we formulate our assumptions regarding future demand and market conditions based on order trends and input from customers regarding their future requirements . if actual market conditions are less favorable than those projected , or if in the future we decide to discontinue sales and marketing of any of our products , additional inventory write-downs may be required . excess and obsolete inventories were written down by $ 649,000 at december 31 , 2019 and $ 718,000 at december 31 , 2018. valuation of intangible and long-lived assets . we evaluate the carrying value of goodwill annually on december 31 , and more frequently if management believes indicators of impairment exist . we assess the impairment of identifiable intangible assets , long lived assets and related goodwill whenever events or changes in circumstances indicate the carrying value may not be recoverable . factors we consider important , which could trigger an impairment review and that we consider when performing our annual goodwill impairment assessment , include the following : significant under-performance relative to expected historical or projected future operating results . significant changes in the manner of our use of the acquired assets or the strategy for our overall business . significant negative industry or economic trends . significant decline in the price of our common stock for a sustained period , and the size of our market capitalization relative to our net book value . for intangible and long-lived assets , if the carrying value exceeds the undiscounted cash flows from such asset . for goodwill , if the carrying value of our net assets ( net book value ) exceeds fair value . 26 when we determine that the carrying value of intangibles , long-lived assets and related goodwill may not be recoverable based upon the existence of one or more of the above indicators of impairment , we measure any potential impairment based on a projected discounted cash flow method using a discount rate that we believe is commensurate with the risk inherent in our current business model . we utilize the income approach to estimate our fair value . the income approach is a valuation technique under which we estimate future cash flows using financial forecasts . future estimated cash flows are discounted to their present value to calculate fair value . when determining fair value , we also give consideration to the control premium in excess of our current market capitalization that might be obtained from a third party acquirer . these assumptions require significant judgment and actual results may differ from assumed or estimated amounts . at december 31 , 2019 , we had goodwill of $ 1.4 million . our recent analysis performed as of december 31 , 2019 indicates that our goodwill is not impaired . however , our conclusion could change in the future , if our assumptions about future economic conditions , revenue growth or profitability change . any resulting impairment charge could have a material effect on our financial position and results of operations in the future . income taxes . significant judgment is required in determining worldwide income tax expense based upon tax laws in the various jurisdictions in which we operate . we have established reserves for uncertain tax positions by applying the “ more likely than not ” threshold ( i.e . , a likelihood of occurrence greater than fifty percent ) . the recognition threshold is met when an entity concludes that a tax position , based solely on its technical merits , is more likely than not to be sustained upon examination by the relevant taxing authority . those tax positions failing to qualify for initial recognition are recognized in the first interim period in which they meet the more likely than not standard , or are resolved through negotiation or litigation with the taxing authority , or upon expiration of the statute of limitations . de-recognition of a tax position that was previously recognized occurs when an entity subsequently determines that a tax position no longer meets the more likely than not threshold of being sustained . all tax positions are analyzed periodically and adjustments are made as events warrant modification , such as the completion of audits or the expiration of statutes of limitations

