Revenue Recognition, and Deferred Revenue and Other Contract Liabilities The Company derives the majority of its product revenue from four primary sources: (i) direct sales under deferred equipment agreements with end-user hospitals where the Company provides up-front monitoring equipment at no up-front charge in exchange for a multi-year sensor purchase commitment, (ii) other direct sales of noninvasive monitoring solutions to end-user hospitals, emergency medical response organizations and other direct customers; (iii) sales of noninvasive monitoring solutions to distributors who then typically resell to end-user hospitals, emergency medical response organizations and other customers; and (iv) sales of integrated circuit boards to OEM customers who incorporate the Companys embedded software technology into their multiparameter monitoring devices. Subject to customer credit considerations, the majority of such sales are made on open account using industry standard payment terms based on the geography within which the specific customer is located. The Company generally recognizes revenue following a single, principles-based five-step model to be applied to all contracts with customers and generally provides for the recognition of revenue in an amount that reflects the consideration to which the Company expects to be entitled, net of allowances for estimated returns, discounts or sales incentives, as well as taxes collected from customers that are remitted to government authorities, when control over the promised goods or services are transferred to the customer. Revenue related to equipment supplied under sales-type lease arrangements is recognized once control over the equipment is transferred to the customer, while revenue related to equipment supplied under operating-type lease arrangements is generally recognized on a straight-line basis over the term of the lease. While the majority of the Companys revenue contracts and transactions contain standard business terms and conditions, there are some transactions that contain non-standard business terms and conditions. As a result, contract interpretation, judgment and analysis is required to determine the appropriate accounting, including: (i) the amount of the total consideration, including variable consideration, (ii) whether the arrangement contains an embedded lease, and if so, whether such embedded lease is a sales-type lease or an operating lease, (iii) the identification of the distinct performance obligations contained within the arrangement, (iv) how the arrangement consideration should be allocated to each performance obligation when multiple performance obligations exist, including the determination of standalone selling price, and (v) when to recognize revenue on the performance obligations. Changes in judgments on these assumptions and estimates could materially impact the timing of revenue recognition. The Company enters into agreements to sell its monitoring solutions and services, sometimes as a part of arrangements with multiple performance obligations that include various combinations of product sales, equipment leases and services. In the case of contracts with multiple performance obligations, the authoritative guidance provides that the total consideration be allocated to each performance obligation on the basis of relative standalone selling prices. When a standalone selling price is not readily observable, the Company estimates the standalone selling price by considering multiple factors including, but not limited to, features and functionality of the product, geographies, type of customer, contractual prices pursuant to Group Purchasing Organization (GPO) contracts, the Companys pricing and discount practices, and other market conditions. Sales under deferred equipment agreements are generally structured such that the Company agrees to provide certain monitoring-related equipment, software, installation, training and/or warranty support at no up-front charge in exchange for the hospitals agreement to purchase sensors over the term of the agreement, which generally ranges from three to six years . The Company allocates contract consideration under deferred equipment agreements containing fixed annual sensor purchase commitments to the underlying lease and non-lease components at contract inception. In determining whether any underlying lease components are related to a sales-type lease or an operating lease, the Company evaluates the customers rights and ability to control the use of the underlying equipment throughout the contract term, including any equipment substitution rights retained by the Company, as well as the Companys expectations surrounding potential contract/lease extensions or renewals and the customers exercise of any purchase options. Revenue allocable to non-lease performance obligations is generally recognized as such non-lease performance obligations are satisfied. Revenue allocable to lease components under sales-type lease arrangements is generally recognized when the lease commences. Revenue allocable to lease components under operating lease arrangements is generally recognized over the term of the operating lease. The Company generally does not expect to derive any significant value in excess of such assets unamortized book value from equipment underlying its operating leases arrangements after the end of the agreement. Revenue from direct sales of products to the Companys end-user hospitals, emergency medical response organizations and other direct customers, as well as to its distributors, is generally recognized upon shipment or delivery to the customer based on the terms of the contract or underlying purchase order. Sales of integrated circuit boards and other products to the Companys OEM customers are generally recognized as revenue at the time of shipment. Revenue related to OEM rainbow  parameter software licenses is generally recognized upon shipment of the OEMs product to its customers, as reported to the Company by the OEM. The Company provides certain customers with various sales incentives that may take the form of discounts or rebates. The Company records estimates related to these programs as a reduction to revenue at the time of sale. In general, customers do not have a right of return for credit or refund. However, the Company allows returns under certain circumstances. At the end of each period, the Company estimates and accrues for these returns as a reduction to revenue. The Company estimates the revenue constraints related to these forms of variable consideration based on various factors, including expected purchasing volumes, prior sales and returns history, and specific contractual terms and limitations. The majority of the Companys royalty and other revenue arose from one agreement that was due and payable quarterly in arrears. An estimate of these royalty revenues was recorded in the period earned based on historical results, adjusted for any new information or trends known to management at the time of estimation. This estimated revenue was adjusted prospectively when the Company received the underlying royalty report, approximately sixty days after the end of the previous quarter. The Company received its final royalty payment from this agreement during the three months ended March 30, 2019. For the three months ended September 28, 2019 and September 29, 2018 , the Company recognized royalty revenue pursuant to this agreement of approximately $0.0 million and $8.1 million , respectively. For the nine months ended September 28, 2019 and September 29, 2018 , the Company recognized royalty revenue pursuant to this agreement of approximately $0.7 million and $25.3 million , respectively. The Company also recognizes revenue from time-to-time related to non-recurring engineering (NRE) services. NRE service revenue is generally recognized over time based on actual costs incurred by the Company.