2ASF4-K4Bluetooth mechanical keyboard

CONFIDENTIALITY REQUEST for Certification Service in USA Federal Communication Commission Equipment Authorization Division, Application Processing Branch 7435 Oakland Mills Road Columbia, MD 21046 Date: 1/8/2020 TO WHOM IT MAY CONCERN Pursuant to Paragraphs §0.457 and 0.459 of the Commission’s Rules (47 C.F.R.) and Section §552(b)(4) of the Freedom of Information Act, we requests confidentiality for the following products: FCC ID Model name 2ASF4-K4 keychron K4 For the product stated above, we request that the following information be held confidential; Exhibits Long-Term Confidentiality Short-Term Confidentiality Short-Term Confidentiality Days External Photos Internal Photos Block Diagram Schematics Test Setup Photos User’s Manual Parts List Tune Up Operational Descriptions The long-term confidentiality exhibits contain our trade secrets and proprietary information that could be of benefit to our competitors. The short-term confidentiality on the basis of ensuring that business sensitive information remains confidential until the actual marketing of our new device. If you have any questions, please feel free to contact me at the address shown below. Sincerely, Signature Nick Ye CEO Shenzhen Bipu Technology, Inc.

Shenzhen Bipu Technology, Inc. 2nd Floor, No. 27, Yangmei Road, Putian Street, Longgang District, Shenzhen, China Federal Communications Commission Authorization and Evaluation Division Equipment Authorization Branch 7435 Oakland Mills Road Columbia, MD 21046 1/8/2020 To whom it may concern: We, Shenzhen Bipu Technology, Inc., the undersigned, hereby authorize Eurofins Product Service GmbH to act on our behalf in all matters relating to applications for equipment authorization FCC ID: 2ASF4-K4including the signing of all documents related to these matters. Any and all acts carried out by Eurofins Product Service GmbH on our behalf shall have the same effect as acts of our own. We also hereby certify that no party to this application is subject to a denial of benefits, including FCC benefits, pursuant to Section 5301 of the Anti-Drug Abuse Act of 1988, 21 U.S.C. 862. Sincerely, Signature Nick Ye CEO Shenzhen Bipu Technology, Inc.

Label & Label Location Size: 50mm(L)*20mm(W) FCC ID: 2ASF4-K4 This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 This report shall not be reproduced except in full, without the written approval of Shenzhen HUAK Testing Technology Co., Ltd. Page 1 of 3 INTERIOR PHOTOGRAPHS OF EUT Fig.1 Fig.2 Bluetooth Antenna Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 This report shall not be reproduced except in full, without the written approval of Shenzhen HUAK Testing Technology Co., Ltd. Page 2 of 3 Fig.3 Fig.4 Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 This report shall not be reproduced except in full, without the written approval of Shenzhen HUAK Testing Technology Co., Ltd. Page 3 of 3 Fig.5 Fig.6

Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 This report shall not be reproduced except in full, without the written approval of Shenzhen HUAK Testing Technology Co., Ltd. Page 1 of 2 RADIO FREQUENCY EXPOSURE Limit According to section 4.3.1 of KDB 447498 D01 General RF Exposure Guidance v06, SAR evaluation is required if the separation distance between the user and/or bystander and the antenna and/or radiating element of the device is less than or equal to 20 cm, except when the device operates at or below the applicable output power level (adjusted for tune-up tolerance) for the specified separation distance defined in Appendix A. Appendix A SAR Test Exclusion Thresholds for 100 MHz – 6 GHz and ≤ 50 mm MHz 5 10 15 20 25 mm 150 39 77 116 155 194 SAR Test Exclusion Threshold (mW) 300 27 55 82 110 137 450 22 45 67 89 112 835 16 33 49 66 82 900 16 32 47 63 79 1500 12 24 37 49 61 1900 11 22 33 44 54 2450 10 19 29 38 48 3600 8 16 24 32 40 5200 7 13 20 26 33 5400 6 13 19 26 32 5800 6 12 19 25 31 MHz 30 35 40 45 50 mm 150 232 271 310 349 387 SAR Test Exclusion Threshold (mW) 300 164 192 219 246 274 450 134 157 179 201 224 835 98 115 131 148 164 900 95 111 126 142 158 1500 73 86 98 110 122 1900 65 76 87 98 109 2450 57 67 77 86 96 3600 47 55 63 71 79 5200 39 46 53 59 66 5400 39 45 52 58 65 5800 37 44 50 56 62 Note: Manufacturer declared that the maximum antenna gain is 1.87dBi (Max.). Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 This report shall not be reproduced except in full, without the written approval of Shenzhen HUAK Testing Technology Co., Ltd. Page 2 of 2 Conducted Power Results Test Mode Channel Frequency (MHz) Measured Peak Output Power (dBm) GFSK 00 2402 -4.064 39 2441 -3.536 78 2480 -4.491 Manufacturing tolerance GFSK (Peak) Channel Channel 0 Channel 39 Channel 78 Target (dBm) -4.5 -4.0 -4.5 Tolerance ±(dB) 1.0 1.0 1.0 Results Test Mode Channel Frequency (MHz) Max. Tune Up Power (dBm, Peak) Max. Eirp including Tune Up (dBm, Peak) Max. Eirp including Tune Up (mW, Peak) Exemption Limit (mW) GFSK 2402 -3.5 -1.63 0.69 10 2440 -3.0 -1.13 0.77 10 2480 -3.5 -1.63 0.69 10 The antenna gain of the EUT for BT is 1.87dBi (Max). the Maximum Eirp is used for Routine Evaluation Exemption according to section 4.3.1 of KDB 447498 D01. So, the SAR evaluation is not required.

Report No.: HK1912203250-E Page 1 of 35 FCC TEST REPORT Test report On Behalf of Shenzhen Bipu Technology, Inc. For Bluetooth mechanical keyboard Model No: keychron K4 FCC ID: 2ASF4-K4 Prepared for : Shenzhen Bipu Technology, Inc. 2nd Floor, No. 27, Yangmei Road, Bantian Street, Longgang District, Shenzhen, China Prepared By : Shenzhen HUAK Testing Technology Co., Ltd. 1F, B2 Building, Junfeng Zhongcheng Zhizao Innovation Park, Fuhai Street, Bao'an District, Shenzhen City, China Date of Test: December 20, 2019~ December 27, 2019 Date of Report: December 27, 2019 Report Number: HK1912203250-E Report No.: HK1912203250-E Page 2 of 35 TEST RESULT CERTIFICATION Applicant’s name ................. : Shenzhen Bipu Technology, Inc. Address .................................. : 2nd Floor, No. 27, Yangmei Road, Bantian Street, Longgang District, Shenzhen, China Manufacture's Name ............ : Shenzhen Bipu Technology, Inc. Address .................................. : 2nd Floor, No. 27, Yangmei Road, Bantian Street, Longgang District, Shenzhen, China Product description Trade Mark ............................. : N/A Product name ........................... : Bluetooth mechanical keyboard Model No ................................ : keychron K4 Standards ............................. : FCC Rules and Regulations Part 15 Subpart C Section 15.247 ANSI C63.10: 2013 This publication may be reproduced in whole or in part for non-commercial purposes as long as the Shenzhen HUAK Testing Technology Co., Ltd. is acknowledged as copyright owner and source of the material. Shenzhen HUAK Testing Technology Co., Ltd. takes no responsibility for and will not assume liability for damages resulting from the reader's interpretation of the reproduced material due to its placement and context. Date of Test ............................. ........... : Date (s) of performance of tests ........... : December 20, 2019~ December 27, 2019 Date of Issue ......................................... : December 27, 2019 Test Result ............................................ : Pass Testing Engineer : (Gary Qian) Technical Manager : (Eden Hu) Authorized Signatory : (Jason Zhou) Report No.: HK1912203250-E Page 3 of 35 Revision History Revision Issue Date Revisions Revised By 00 December 27, 2019 Initial Issue Jason Zhou Report No.: HK1912203250-E Page 4 of 35 TABLE OF CONTENTS Description Page 1. GENERAL INFORMATION ................................................................................................................ 5 1.1. Description of Device (EUT) ................................................................................................................... 5 1.2 Support equipment List ................................................................................................................................ 5 1.3 EUT configuration ......................................................................................................................................... 5 1.4 External I/O Cable ........................................................................................................................................ 5 1.5 Description of Test Facility .......................................................................................................................... 5 1.6 Statement of the Measurement Uncertainty ............................................................................................. 6 1.7 Measurement Uncertainty ........................................................................................................................... 6 1.8 Description of Test Modes .......................................................................................................................... 6 2. TEST METHODOLOGY ...................................................................................................................... 7 2.1 EUT Configuration ........................................................................................................................................ 7 2.2 EUT Exercise ................................................................................................................................................ 7 2.3 General Test Procedures ............................................................................................................................ 7 2.4. Test Sample ................................................................................................................................................. 7 3. SYSTEM TEST CONFIGURATION .................................................................................................. 8 3.1 Justification .................................................................................................................................................... 8 3.2 EUT Exercise Software ............................................................................................................................... 8 3.3 Special Accessories ..................................................................................................................................... 8 3.4 Block Diagram/Schematics ......................................................................................................................... 8 3.5 Equipment Modifications ............................................................................................................................. 8 3.6 Test Setup ..................................................................................................................................................... 8 4. SUMMARY OF TEST RESULTS ....................................................................................................... 9 5. SUMMARY OF TEST EQUIPMENT ............................................................................................... 10 6. MEASUREMENT RESULTS .......................................................................…

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Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 1 of 19 Appendix A RF Test Data for BT(BDR/EDR) (Conducted Measurement) Product Name: Bluetooth mechanical keyboard Trade Mark: N/A Test Model: keychron K4 FCC ID: 2ASF4-K4 Environmental Conditions Temperature: 22.8 C Relative Humidity: 50% ATM Pressure: 100.0 kPa Test Engineer: Gary Qian Supervised by: Eden Hu A.1 20 dB Bandwidth Mode Channel. 20dB Bandwidth [MHz] Limit(MHz) Verdict GFSK LCH 1.084 Not Specified PASS GFSK MCH 1.108 Not Specified PASS GFSK HCH 1.020 Not Specified PASS Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 2 of 19 Test Graph Graphs GFSK/LCH GFSK/MCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 3 of 19 GFSK/HCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 4 of 19 A.2 Dwell Time Mode Packet Chann el Burst Width [s/hop/ch] Total Hops[hop*ch] Dwell Time[s] Limit [s] Verdict GFSK DH5 LCH 0.002904 106.7 0.309871 0.4 PASS GFSK DH5 MCH 0.002901 106.7 0.309498 0.4 PASS GFSK DH5 HCH 0.002900 106.7 0.309393 0.4 PASS Test Graph Graphs GFSK_DH5/LCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 5 of 19 GFSK_DH5/MCH GFSK_DH5/HCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 6 of 19 A.3 Carrier Frequency Separation Mode Channel. Carrier Frequency Separation [MHz] Limit [MHz] Verdict GFSK LCH 0.991 0.72 PASS GFSK MCH 0.999 0.74 PASS GFSK HCH 0.994 0.68 PASS Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 7 of 19 Test Graph Graphs GFSK/LCH GFSK/MCH GFSK/HCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 8 of 19 A.4 Hopping Channel Number Mode Channel. Number of Hopping Channel[N] Limit[N] Verdict GFSK Hop 79 >=15 PASS Test Graph Graphs GFSK/Hop Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 9 of 19 A.5 Conducted Peak Output Power Mode Channel. Maximum Peak Output Power [dBm] Limit [dBm] Verdict GFSK LCH -4.064 21 PASS GFSK MCH -3.536 21 PASS GFSK HCH -4.491 21 PASS Test Graph Graphs GFSK/LCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 10 of 19 GFSK/MCH GFSK/HCH Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 11 of 19 A.6 Band-edge for RF Conducted Emissions Type Carrier Frequency(MHz) Frequency(MHz) Carrier Frequency Power [dBm] Bandedge Peak(dBm) Upper limit(dBm) Conclusion 1DH5 2402 2400 -4.513 -59.79 -24.513 Pass 1DH5 2480 2495.034 -4.307 -58.199 -24.307 Pass 1DH5-Hopping 2402 2399.79 -3.434 -48.695 -23.434 Pass 1DH5-Hopping 2480 2500 -3.605 -58.643 -23.605 Pass Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 12 of 19 Test Graph Graphs GFSK/LCH/No Hop GFSK/HCH/No Hop Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 13 of 19 GFSK/LCH/Hop GFSK/HCH/Hop Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 14 of 19 A.7 RF Conducted Spurious Emissions Test Graph GFSK_LCH_Graphs Pref Puw Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 15 of 19 GFSK_MCH_Graphs Pref Puw Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 16 of 19 GFSK_HCH_Graphs Pref Puw Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 17 of 19 A.8 Restrict-band band-edge measurements Type Carrier Frequency (MHz) Gain (dBi) Ground Factor(dB) Peak Value(dBm) E Limit Conclusion Frequency [dBuV/m] [dBuV/m] (MHz) 1DH5 2402 2390 2.00 0.00 -52.033 45.167 74 Pass 1DH5 2480 2496.453 2.00 0.00 -48.460 48.74 74 Pass Type Carrier Frequency (MHz) Gain (dBi) Ground Factor(dB) Average Value(dBm) E Limit Conclusion Frequency [dBuV/m] [dBuV/m (MHz) 1DH5 2402 2390 2.00 0.00 -60.405 36.795 54 Pass 1DH5 2480 2496.453 2.00 0.00 -58.272 38.928 54 Pass Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 18 of 19 Restrict-band band-edge measurements_2402_PEAK_DH5 Restrict-band band-edge measurements_2402_AV_DH5 Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Report No.: HK1912203250-E Page 19 of 19 Restrict-band band-edge measurements_2480_PEAK_DH5 Restrict-band band-edge measurements_2480_AV_DH5

Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 TEST SETUP PHOTOS OF THE EUT Radiated Emission Below 1GHz Radiated Emission Above 1GHz Shenzhen HUAK Testing Technology Co., Ltd. FCC ID: 2ASF4-K4 Conducted Emission