NOTE C – PATENTS

The include patents with estimated remaining economic useful lives ranging from 1.75 to 12 years. For all periods presented, all of the Company’s patents were subject to amortization. The gross carrying amounts and accumulated amortization related to acquired intangible assets as of September, 2021 and December 31, 2020 were as follows

NOTE C – PATENTS (continued)

Amortization expense for the three months ended September 30, 2021 and 2020 was $74,000 and $72,000, respectively. Amortization expense for the nine months ended September 30, 2021 and 2020 was $221,000 and $216,000, respectively. Future amortization of intangible assets, net is as follows:

The Company’s Remote Power Patent expired on March 7, 2020. All of the patents within the Company’s Mirror Worlds Patent Portfolio have expired. All of the patents within the Cox Patent Portfolio expired in September 2021 except for two patents which expire in July 2023 and November 2023. The expiration dates of patents within the Company’s M2M/IoT Patent Portfolio range from September 2033 to May 2034.