Document ID: FAA-2012-0686-0001
Agency: faa
Document Type: Notice
Title: Technical Standard Orders: Equipment that Prevent Blocked Channels Used in Two-way Radio Communications Due to Simultaneous Transmissions
Posted Date: 2012-06-22T04:00Z

[Federal Register Volume 77, Number 121 (Friday, June 22, 2012)]
[Notices]
[Page 37734]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-15238]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

Technical Standard Order (TSO) C-122a, Equipment That Prevent 
Blocked Channels Used in Two-Way Radio Communications Due to 
Simultaneous Transmissions

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice.

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SUMMARY: This notice announces the FAA's intent to cancel TSO-C122a, 
Equipment That Prevent Blocked Channels Used in Two-Way Radio 
Communications Due to Simultaneous Transmissions. The effect of the 
cancelled TSO will not affect design or production according to an 
existing TSO authorization (TSOA). Articles produced under an existing 
TSOA can still be installed according to existing airworthiness 
approvals and applications for new airworthiness installation approvals 
will still be processed.

DATES: Comments must be received on or before July 23, 2012.

FOR FURTHER INFORMATION CONTACT: Mrs. Veronica Gardner, AIR-130, 
Federal Aviation Administration, 470 L'Enfant Plaza, Suite 4102, 
Washington, DC 20024. Telephone (202) 385-4690, fax (202) 385-4651, 
email to: veronica.gardner@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    You are invited to comment on the proposed cancellation of the TSO 
by submitting written data, views, or arguments to the above address. 
Comments received may be examined, both before and after the closing 
date at the above address, weekdays except federal holidays, between 
8:30 a.m. and 4:30 p.m. The Director, Aircraft Certification Service, 
will consider all comments received on or before the closing date.

Background

    In 1984, the FAA was petitioned to enact rulemaking requiring two-
way radio communication systems employing anti-blocking and stuck 
microphone protection circuitry. Our response to this rulemaking 
petition was the issuance of TSO-C128, Devices that Prevent Blocked 
Channels Used in Two-Way Radio Communications Due to Unintentional 
Transmissions, for preventing blocked channels used in two-way radio 
communication due to unintentional transmissions. TSO-C128, and the 
subsequent revision, has proven effective and popular with VHF radio 
manufacturers. Since 1994, there has been only one application for TSOA 
for TSO-C122a. Therefore, we believe it is appropriate to cancel TSO-
C122a, given the eventual obsolescence of TSO-C122a equipment and the 
lack of industry interest in new TSO-C122a product designs. We continue 
to coordinate with industry's federal advisory committee through RTCA 
Special Committee (SC) 226, Audio Systems and Equipment, for any new 
developments on other means being used to address blocked channels 
caused by simultaneous transmissions.

    Issued in Washington, DC, on June 18, 2012.
Susan J.M. Cabler,
Assistant Manager, Aircraft Engineering Division, Aircraft 
Certification Service.
[FR Doc. 2012-15238 Filed 6-21-12; 8:45 am]
BILLING CODE 4910-13-P