2A63XKST-620Wireless headphone

Shenzhen Huijinzhicheng Technology Co., Limited 2026.08.05 Eurofins Electrical and Electronic Testing NA, Inc. 914 West Patapsco Avenue Baltimore, MD 21230 RE: Attestation Statements Part 2.911(d)(5)(i) request for FCC ID: 2A63XKST-620 [Shenzhen Huijinzhicheng Technology Co., Limited] certifies that the equipment for which authorization is sought is not “covered” equipment prohibited from receiving an equipment authorization pursuant to section 2.903 of the FCC rules. We also certify that, as of the date of the filing of the application, the equipment does not utilize cyber-security or anti-virus software from Kaspersky Lab, Inc, or any of its successors and assignees, which is also on the “covered list”. Sincerely, (Applicant signature) (Applicant printed name) Kunta Chen Shenzhen Huijinzhicheng Technology Co., Limited 2026.08.05 Eurofins Electrical and Electronic Testing NA, Inc. 914 West Patapsco Avenue Baltimore, MD 21230 RE: Attestation Statements Part 2.911(d)(5)(ii) request for FCC ID: 2A63XKST-620 [Shenzhen Huijinzhicheng Technology Co., Limited] certifies that, as of the date of the filing of the application, the applicant is not identified on the Covered List as an entity producing “covered” equipment. Sincerely, (Applicant signature) (Applicant printed name) Kunta Chen

Shenzhen Huijinzhicheng Technology Co., Limited 2026.08.05 Eurofins Electrical and Electronic Testing NA, Inc. 914 W. Patapsco Avenue Baltimore, MD 21230 USA RE: CONFIDENTIALITY REQUEST FOR EUT NAME: Wireless headphone MODEL: KST-620, KST-620ANC, KST-620+TX3, KST-620+TX2, KST-620+TX FCC ID: 2A63XKST-620 To Whom It May Concern: This letter serves as an official request for confidentiality under sections 0.457 and 0.459 of CFR 47. We have requested that the - Block Diagram - Schematics - Operational Description required to be submitted with this application be permanently withheld from public review. The above materials contain trade secrets and proprietary information not customarily released to the public. The public disclosure of these materials may be harmful to the applicant and provide unjustified benefits to its competitors. Please contact me if there is any information you may need. Sincerely, Client’s signature: Client’s name / title: Kunta Chen / Manager Contact information / address: Room 412, 4rd Floor, No. 330, Pinghu Street, Longgang District, Shenzhen, China

Shenzhen Huijinzhicheng Technology Co., Limited 2026.08.05 Eurofins Electrical and Electronic Testing NA, Inc. 914 W. Patapsco Avenue Baltimore, MD 21230 USA RE: LETTER OF AGENT AUTHORIZATION To Whom It May Concern: We, the undersigned, hereby authorize Shenzhen BCTC Technology Co., Ltd. to act on our behalf in all matters relating to application for equipment authorization, including the signing of all documents relating to these matters. We also hereby certify that no party to the application authorized hereunder is subject to the denial of benefits, including FCC benefits, pursuant to Section 5301 of the Anti-Drug Abuse Act of 1988, 21 U.S.C.853(a). This agreement expires one year from the current date. Sincerely, Client’s signature: Client’s name / title: Kunta Chen / Manager Contact information / address: Room 412, 4rd Floor, No. 330, Pinghu Street, Longgang District, Shenzhen, China

Shenzhen Huijinzhicheng Technology Co., Limited Model Difference 2026.08.05 EUT NAME: Wireless headphone MODEL: KST-620, KST-620ANC, KST-620+TX3, KST-620+TX2, KST-620+TX FCC ID: 2A63XKST-620 Our production units bearing the following model numbers are identical in circuitry and electrical, mechanical and physical construction; The difference is only in model names. Regards Sincerely Client’s signature: Client’s name / title: Kunta Chen / Manager Contact information / address: Room 412, 4rd Floor, No. 330, Pinghu Street, Longgang District, Shenzhen, China

External Photos

Size:10*5m FCC ID: 2A63XKST-620 Label Location

Internal Photos Antenna

FCC ID: 2A63XKST-620 Portable device According to §15.247(e)(i) and §1.1307(b)(1), systems operating under the provisions of this section shall be operated in a manner that ensures that the public is not exposed to radio frequency energy level in excess of the Commission’s guidelines. According to KDB447498 D01 General RF Exposure Guidance V06 The 1-g SAR and 10-g SAR test exclusion thresholds for 100 MHz to 6 GHz at test separation distances ≤ 50 mm are determined by: [(max. power of channel, including tune-up tolerance, mW)/(min. test separation distance, mm)]·[√f(GHZ)] ≤ 3.0 for 1-g SAR and ≤ 7.5 for 10-g extremity SAR, where: • f(GHZ) is the RF channel transmit frequency in GHz • Power and distance are rounded to the nearest mW and mm before calculation • The result is rounded to one decimal place for comparison When the minimum test separation distance is < 5 mm, a distance of 5 mm is applied to determine SAR test exclusion. BT Modulation Channel Freq. (GHz) Conduct ed power (dBm) Conducte d power (mW) Tune-up power (dBm) Max tune-up power (dBm) Max tune-up power (mW) Distance (mm) Result calculatio n SAR Exclusion threshold SAR test exclusion GFSK 2.441 1 1.26 1±1 2.00 1.58 <5 0.49524 3.00 YES π/ 4 DQPSK 2.441 1.92 1.56 1±1 2.00 1.58 <5 0.49524 3.00 YES 8DPSK 2.441 2.44 1.75 2±1 3.00 2.00 <5 0.62347 3.00 YES BLE Modulation Channel Freq. (GHz) Conduct ed power (dBm) Conducte d power (mW) Tune-up power (dBm) Max tune-up power (dBm) Max tune-up power (mW) Distance (mm) Result calculatio n SAR Exclusion threshold SAR test exclusion GFSK(1M bps) 2.440 1.02 1.26 1±1 2.00 1.58 <5 0.49514 3.00 YES Conclusion: For the max result : 0.62347＜3, the SAR testing is not required.

Inverted F Antenna Specification Summary ITEM ANT SPEC Model Name 2.4G ANT Horizontal Vertical 2400MHz 2400MHz2500MHz2400MHz2400MHz 2500MHz Center Frequency -1.26 -0.76 -0.58 -5.25 -2.46 -1.86 MAX. Gain -0.58dB Polarization Horizontal and Vertical Azimuth Beam Pattern Omni-directional Impedance 50 Ohm Antenna Length 38.20mm Manufacture ZHUHAI JIELI TECHNOLOGY CO.,LTD Antenna Photo & Length (mm) Horizontal: 2400 MHz 2450 MHz 2500 MHz Power (dBm) Max: 0 Min: -40 Scale: 5/div Gain(dB) Frequency (MHz) Max Min Avg 2400 -1.26174 -30.0801 -7.18716 2450 -0.765802 -36.5604 -7.48023 2500 -0.585582 -22.0315 -6.59127 Vertical: 2400 MHz 2450 MHz 2500 MHz Power (dBm) Max: 0 Min: -30 Scale: 5/div Gain(dB) Frequency (MHz) Max Min Avg 2400 -5.2537 -22.1424 -12.4294 2450 -2.4652 -24.5837 -10.4702 2500 -1.86120 -29.5214 -9.20432 ANT Test Labs：Attestation of Global Compliance Co., Ltd.

No.：BCTC/KJ-RF-ICT-001 Page 1 of 87 Edition：B.1 TEST REPORT Shenzhen BCTC Technology Co., Ltd. Report No.: BCTC2606036452E Applicant: Shenzhen Huijinzhicheng Technology Co., Limited Product Name: Wireless headphone Test Model: KST-620 Tested Date: 2026-06-02 to 2026-06-12 Issued Date: 2026-07-06 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 2 of 87 Edition：B.1 FCC ID: 2A63XKST-620 The test report is effective only with both signature and specialized stamp.This result(s) shown in this report refer only to the sample(s) tested. Without written approval of Shenzhen BCTC Technology Co., Ltd, this report can’t be reproduced except in full.The tested sample(s) and the sample information are provided by the client. Product Name: Wireless headphone Trademark: Electro-Harmonix Model/Type Reference: KST-620, KST-620ANC, KST-620+TX3, KST-620+TX2, KST-620+TX Prepared For: Shenzhen Huijinzhicheng Technology Co., Limited Address: Room 412, 4rd Floor, No. 330, Pinghu Street, Longgang District, Shenzhen, China Manufacturer: Shenzhen Huijinzhicheng Technology Co., Limited Address: Room 412, 4rd Floor, No. 330, Pinghu Street, Longgang District, Shenzhen, China Prepared By: Shenzhen BCTC Technology Co., Ltd. Address: Room 101M, Unit 1, Building1, Pengyuan, No.18, Lilang Road, Shanglilang, Nanwan Subdistrict, Longgang District, Shenzhen, Guangdong, China. Sample Received Date: 2026-05-29 Sample Tested Date: 2026-06-02 to 2026-06-12 Report No.: BCTC2606036452E Test Standards FCC Part15.247 ANSI C63.10-2020 Test Results PASS Remark: This is Bluetooth Classic radio test report. Prepared by : Reviewer by : Approved by: Eric Yang Mike Zheng Sewen Guo Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 3 of 87 Edition：B.1 Table of Content Test Report Declaration Page 1. Version .................................................................................................................. 5 2. Test Summary ....................................................................................................... 6 3. Measurement Uncertainty ..................................................................................... 7 4. Product Information and Test Setup ...................................................................... 8 4.1 Product Information ............................................................................................... 8 4.2 Test Setup Configuration ...................................................................................... 8 4.3 Support Equipment ............................................................................................... 9 4.4 Channel List .......................................................................................................... 9 4.5 Test Mode ........................................................................................................... 10 4.6 Table Of Parameters Of Text Software Setting ................................................... 10 5. Test Facility And Test Instrument Used ............................................................... 11 5.1 Test Facility ......................................................................................................... 11 5.2 Test Instrument Used .......................................................................................... 11 6. Conducted Emissions .......................................................................................... 13 6.1 Block Diagram Of Test Setup .............................................................................. 13 6.2 Limit .................................................................................................................... 13 6.3 Test procedure .................................................................................................... 13 6.4 EUT operating Conditions ................................................................................... 13 6.5 Test Result .......................................................................................................... 14 7. Radiated emissions ............................................................................................. 16 7.1 Block Diagram Of Test Setup .............................................................................. 16 7.2 Limit .................................................................................................................... 17 7.3 Test procedure .................................................................................................... 18 7.4 EUT operating Conditions ................................................................................... 19 7.5 Test Result .......................................................................................................... 20 8. Radiated Band Emission Measurement and Restricted Bands of Operation ...... 26 8.1 Block Diagram Of Test Setup .............................................................................. 26 8.2 Limit .................................................................................................................... 26 8.3 Test procedure .................................................................................................... 27 8.4 EUT operating Conditions ................................................................................... 27 8.5 Test Result .......................................................................................................... 28 9. Spurious RF Conducted Emissions ..................................................................... 29 9.1 Block Diagram Of Test Setup .............................................................................. 29 9.2 Limit .................................................................................................................... 29 9.3 Test procedure .................................................................................................... 29 9.4 Test Result ..................................…

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Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 55 of 87 Edition：B.1 OBW NVNT 2-DH5 2441MHz Ant1 OBW NVNT 2-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 56 of 87 Edition：B.1 OBW NVNT 3-DH5 2402MHz Ant1 OBW NVNT 3-DH5 2441MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 57 of 87 Edition：B.1 OBW NVNT 3-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 58 of 87 Edition：B.1 11. Maximum Peak Output Power 11.1 Block Diagram Of Test Setup 11.2 Limit FCC Part15 (15.247) , Subpart C Section Test Item Limit Frequency Range (MHz) Result 15.247(b)(1) Peak Output Power 0.125 watt or 21dBm 2400-2483.5 PASS 11.3 Test procedure 1. Remove the antenna from the EUT and then connect a low RF cable from the antenna port to the spectrum. 2. Set the spectrum analyzer: RBW = 2MHz. VBW = 6MHz. Sweep = auto; Detector Function = Peak. 3. Keep the EUT in transmitting at lowest, medium and highest channel individually. Record the max value. 11.4 Test Result Condition Mode Frequency (MHz) Conducted Power (dBm) Limit (dBm) Verdict NVNT 1-DH5 2402 0.92 21 Pass NVNT 1-DH5 2441 1 21 Pass NVNT 1-DH5 2480 0.32 21 Pass NVNT 2-DH5 2402 1.86 21 Pass NVNT 2-DH5 2441 1.92 21 Pass NVNT 2-DH5 2480 1.23 21 Pass NVNT 3-DH5 2402 2.39 21 Pass NVNT 3-DH5 2441 2.44 21 Pass NVNT 3-DH5 2480 1.72 21 Pass Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 59 of 87 Edition：B.1 Test Graphs Power NVNT 1-DH5 2402MHz Ant1 Power NVNT 1-DH5 2441MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 60 of 87 Edition：B.1 Power NVNT 1-DH5 2480MHz Ant1 Power NVNT 2-DH5 2402MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 61 of 87 Edition：B.1 Power NVNT 2-DH5 2441MHz Ant1 Power NVNT 2-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 62 of 87 Edition：B.1 Power NVNT 3-DH5 2402MHz Ant1 Power NVNT 3-DH5 2441MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 63 of 87 Edition：B.1 Power NVNT 3-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 64 of 87 Edition：B.1 12. Hopping Channel Separation 12.1 Block Diagram Of Test Setup 12.2 Limit Frequency hopping systems shall have hopping channel carrier frequencies separated by a minimum of 25 kHz or the 20 dB bandwidth of the hopping channel, whichever is greater. Alternatively, frequency hopping systems operating in the 2400-2483.5 MHz band may have hopping channel carrier frequencies that are separated by 25 kHz or two-thirds of the 20 dB bandwidth of the hopping channel, whichever is greater, provided the systems operate with an output power no greater than 0.125W. 12.3 Test procedure 1. Remove the antenna from the EUT and then connect a low RF cable from the antenna port to the spectrum. 2. Set the spectrum analyzer: RBW = 30kHz. VBW = 100kHz , Span = 2.0MHz. Sweep = auto; Detector Function = Peak. Trace = Max hold. 3. Allow the trace to stabilize. Use the marker-delta function to determine the separation between the peaks of the adjacent channels. The limit is specified in one of the subparagraphs of this Section Submit this plot. 12.4 Test Result Condition Mode Hopping Freq1 (MHz) Hopping Freq2 (MHz) HFS (MHz) Limit (MHz) Verdict NVNT 1-DH5 2402.017 2403.001 0.984 0.634 Pass NVNT 1-DH5 2441.002 2442.019 1.017 0.622 Pass NVNT 1-DH5 2479.008 2480.001 0.993 0.627 Pass NVNT 2-DH5 2402.017 2403.016 0.999 0.852 Pass NVNT 2-DH5 2440.858 2442.007 1.149 0.849 Pass NVNT 2-DH5 2479.008 2480.019 1.011 0.843 Pass NVNT 3-DH5 2402.005 2403.019 1.014 0.875 Pass NVNT 3-DH5 2441.017 2442.016 0.999 0.897 Pass NVNT 3-DH5 2479.008 2480.01 1.002 0.848 Pass Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 65 of 87 Edition：B.1 Test Graphs CFS NVNT 1-DH5 2402MHz Ant1 CFS NVNT 1-DH5 2441MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 66 of 87 Edition：B.1 CFS NVNT 1-DH5 2480MHz Ant1 CFS NVNT 2-DH5 2402MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 67 of 87 Edition：B.1 CFS NVNT 2-DH5 2441MHz Ant1 CFS NVNT 2-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 68 of 87 Edition：B.1 CFS NVNT 3-DH5 2402MHz Ant1 CFS NVNT 3-DH5 2441MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 69 of 87 Edition：B.1 CFS NVNT 3-DH5 2480MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 70 of 87 Edition：B.1 13. Number of Hopping Frequency 13.1 Block Diagram Of Test Setup 13.2 Limit Frequency hopping systems in the 2400-2483.5 MHz band shall use at least 15 channels. 13.3 Test procedure 1. Remove the antenna from the EUT and then connect a low RF cable from the antenna port to the spectrum. 2. Set the spectrum analyzer: RBW = 100kHz. VBW = 300kHz. Sweep = auto; Detector Function = Peak. Trace = Max hold. 3. Allow the trace to stabilize. It may prove necessary to break the span up to sections. in order to clearly show all of the hopping frequencies. The limit is specified in one of the subparagraphs of this Section. 4. Set the spectrum analyzer: Start Frequency = 2.4GHz, Stop Frequency = 2.4835GHz. Sweep=auto; 13.4 Test Result Condition Mode Hopping Number Limit Verdict NVNT 1-DH5 79 15 Pass NVNT 2-DH5 79 15 Pass NVNT 3-DH5 79 15 Pass Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 71 of 87 Edition：B.1 Test Graphs Hopping No. NVNT 1-DH5 2402MHz Ant1 Hopping No. NVNT 2-DH5 2402MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 72 of 87 Edition：B.1 Hopping No. NVNT 3-DH5 2402MHz Ant1 Report No.:BCTC2606036452E No.：BCTC/KJ-RF-ICT-001 Page 73 of 87 Edition：B.1 14. Dwell Time 14.1 Block Diagram Of Test Setup 14.2 Limit Frequency hopping systems in the 2400-2483.5 MHz band shall use at least 15 channels. The average time of occupancy on any channel shall not be greater than 0.4 seconds within a period of 0.4 seconds multiplied by the number of hopping channels employed. Frequency hopping systems may avoid or suppress transmissions on a particular hopping frequency provided that a minimum of 15 channels are us…

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