Note C – Patents

The Company’s intangible assets at December 31, 2023 include patents with estimated remaining economic useful lives ranging from 10 to 16 years. For all periods presented, all the Company’s patents were subject to amortization. The gross carrying amounts and accumulated amortization related to acquired intangible assets as of December 31, 2023 and 2022 were as follows:

Amortization expense for the years ended December 31, 2023 and 2022 was $266,000 and $316,000, respectively. Future amortization of current intangible assets, net is as follows:

The expiration dates for the M2M/IoT Portfolio range from September 2033 to May 2034. The expiration dates within the Company’s HFT Patent Portfolio range from October 31, 2039 to November 1, 2039. All of the patents within the Company’s Mirror Worlds Patent Portfolio, Cox Portfolio and the Remote Power Patent have expired.