SIC 3661 — Telephone and Telegraph Apparatus
Official OSHA SIC Manual Definition
Establishments primarily engaged in manufacturing wire telephone and telegraph equipment. Included are establishments manufacturing modems and other telephone and telegraph communications interface equipment. Establishments primarily engaged in manufacturing cellular radio telephones are classified in Industry 3663.
Description & Classification
SIC code 3661 representing 'Telephone and Telegraph Apparatus' is an industry category in the Standard Industrial Classification (SIC) system under U.S. OSHA and Federal procurement registers.
Modern NAICS Crosswalk
Trace the modern equivalent classifications in the 2022 North American Industry Classification System (NAICS) database:
- NAICS 334418 - Printed Circuit Assembly (Electronic Assembly) Manufacturing (via SIC1987:3661→NAICS1997:334418→2002:334418→2007:334418→2012:334418→2017:334418→2022:334418)
- NAICS 334210 - Telephone Apparatus Manufacturing (via SIC1987:3661→NAICS1997:33421→2002:334210→2007:334210→2012:334210→2017:334210→2022:334210)
Classification Details
| SIC Code | 3661 |
|---|---|
| Industry Title | Telephone and Telegraph Apparatus |
| Division | Division D: Manufacturing |
| Major Group | Major Group 36: Electronic and Other Electrical Equipment and Components |
| JSON Endpoint | View as JSON · API → |
| Source / Verified | US Census 1987 SIC Concordance / 2026-08-08 |
SIC vs NAICS Compliance & Common Mismatches
Legacy SIC code 3661 classifies commercial operations based on primary end-product or service output under the 1987 federal framework. In contrast, modern 2022 NAICS codes group establishments based on production process inputs.
When submitting public disclosures to SEC EDGAR or determining OSHA workplace safety log recordkeeping exemptions (29 CFR Part 1904), rely strictly on the official OSHA 4-digit SIC classification rather than an automated commercial translation.
💡 Expert Guidance: SIC to NAICS Conversion
Common Compliance Mistake: Many contractors and B2B analysts confuse legacy 4-digit SIC codes like 3661 with modern 6-digit NAICS codes. Ensure that you use the correct active 2022 NAICS code (e.g. from the crosswalk below) when submitting representations on SAM.gov, as federal contracting officers only accept modern NAICS codes.
Related Pages & Tools
Further regulatory reference links for legacy SIC code 3661:
- SIC Codes Complete Compliance Guide — Detailed history and active legal applications of the SIC classification framework.
- Why Legacy SIC Codes Persist Guide — How credit systems and the SEC still rely on SIC metadata.
- SIC ↔ NAICS Crosswalk Tool — Trace industrial code conversions dynamically.
- SIC 3661 to NAICS Crosswalk — Bidirectional mapping to modern NAICS codes (Telephone and Telegraph Apparatus).
- SIC Major Group 36 Hub — View other legacy industries in this business division.
Frequently Asked Questions (FAQ)
What industry sector is represented by legacy SIC code 3661? ▾
Legacy SIC code 3661 represents 'Telephone and Telegraph Apparatus', categorized under Division Division D: Manufacturing and Major Group Major Group 36: Electronic and Other Electrical Equipment and Components. The Standard Industrial Classification (SIC) system was developed in the late 1930s.
What is the modern 2022 NAICS equivalent for legacy SIC 3661? ▾
Legacy SIC code 3661 maps to the modern 2022 NAICS industry classifications: NAICS 334418 (Printed Circuit Assembly (Electronic Assembly) Manufacturing), NAICS 334210 (Telephone Apparatus Manufacturing). Mappings are resolved transitively across successive updates to handle splits.
Why do credit agencies and banks still reference legacy SIC code 3661? ▾
Registries like Dun & Bradstreet, insurance underwriters, and private platforms retain SIC code 3661 because their historical financial risk data and scoring models are indexed using the legacy 4-digit SIC framework.
Does the SEC EDGAR system allow searching public filings by SIC 3661? ▾
Yes. The SEC Division of Corporation Finance assigns a primary 4-digit SIC code to public companies. You can search the EDGAR database using SIC code 3661 to group reporting peer firms.
How do OSHA safety recordkeeping rules apply to SIC code 3661? ▾
Under 29 CFR Part 1904 safety regulations, OSHA references legacy SIC codes including 3661 to determine if a physical establishment is required to maintain daily injury logs (Form 300) or is partially exempt.
What is the structural difference between SIC 3661 and NAICS codes? ▾
SIC code 3661 classifies establishments based on their final product output or market destination (what they sell), while modern NAICS codes classify them based on production processes and inputs (how they work).
What are the typical business activities classified under legacy SIC 3661? ▾
Typical business activities classified under legacy SIC 3661 are the operations associated with 'Telephone and Telegraph Apparatus'. Mapped modern NAICS codes can be referenced for specific current examples.
Is legacy SIC code 3661 uniform across all 50 U.S. states? ▾
Yes, the Standard Industrial Classification (SIC) system, including code 3661, was published as a federal standard and remains uniform nationwide. It is still referenced by various state workers' compensation boards and departments of labor.
Sources & References
- U.S. Department of Labor (OSHA): OSHA Standard Industrial Classification (SIC) Manual — Code 3661
- U.S. Census Bureau: 1987 SIC to 2022 NAICS Concordance Tables
- Federal Reserve Board: Industrial Production & Capacity Utilization Classifications
- Internal Revenue Service (IRS): Schedule C Principal Business Activity (PBA) Industry Concordance
- Office of Management and Budget (OMB): Standard Industrial Classification Systems Governance