7. Commitments and Contingencies Operating Leases The Company rents its office and laboratory facilities in Mountain View, California under an operating lease which has been extended until January 2020, with an option to extend the lease for another five years. We also lease approximately 3,300 square feet of office space in London, England. That lease ends in June 2020, but the Company has an option to exit the lease in 2015. Rent expense on a straight-line basis was as follows (in thousands): Years Ended December 31, 2013 2012 2011 Rent expense $ 2,310 $ 2,280 $ 2,231 At December 31, 2013, future minimum payments under the leases are as follows (in thousands): Years ended December 31, Future Minimum Lease Payments 2014 $ 2,149 2015 1,979 2016 2,140 2017 2,205 Thereafter 4,415 Total $ 12,888 Warranties The Company generally provides one year of post-contract customer service on the sale of its systems. Post-contract customer service revenue is recognized ratably over the term of the service period and associated expenses are charged to cost of revenues as incurred. The Company provides a limited warranty on the sale of catheters and records a warranty reserve at the time of sale to cover the estimated warranty costs. The Company s warranty obligation may be impacted by product failure rates, material usage and service costs associated with its warranty obligations. The Company periodically evaluates and adjusts the warranty reserve to the extent actual warranty expense differs from the original estimates. Movement in the warranty liability was as follows (in thousands): Years Ended December 31, 2013 2012 Balance at beginning of period $ 9 $ 12 Warranties issued during the period 105 112 Warranty costs incurred during the period (105 ) (115 ) Balance at end of period $ 9 $ 9 Other The Company has minimum royalty obligations of $100,000 per year under a license agreement with Mitsubishi Electric Research Laboratories, Inc. which reduces to $55,000 per year if the license becomes non-exclusive. The royalty obligati