Product Overview
Archer Radio Shack 75491 / RS-501 MOS-to-LED Interface IC
Condition
New old stock. Unopened vintage packaging with attached paper specification sheet on reverse. Sealed unit contains one 14-pin DIP integrated circuit marked ITT 491 with date code 7415.
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Product Overview
Archer catalog number 276-1701 (Radio Shack RS-501) is a quad LED segment driver integrated circuit equivalent to the industry-standard 75491. Designed to interface MOS logic outputs with common-cathode LED displays in multiplexed systems, it integrates four independent high-gain Darlington transistor pairs into a standard 14-pin dual in-line package.
Key Features
- Four independent Darlington driver channels
- 50 mA source or sink capability per segment
- Compatible with low-current MOS logic inputs
- Standard 14-pin DIP package
- Internal chip markings: ITT 491, date code 7415
- Attached manufacturer specification sheet on packaging reverse
Applications
- Restoring vintage digital clocks, frequency counters, and test gear using 1970s MOS display circuits
- Interfacing low-power microcontroller logic to multi-digit seven-segment LED readouts in custom hobby builds
- Driving discrete indicator arrays or multiplexed common-cathode displays on retro computing projects
Frequently Asked Questions
What is the pin count and package type?
This is a standard 14-pin dual in-line package (DIP-14) suitable for solder breadboards, perfboards, or standard IC sockets.
What industry-standard part number does this replace?
This chip functions as a commercial equivalent to the standard 75491 and SN75491 quad LED segment driver.
Why buy this specific vintage unit?
This listing provides an individually verified, unopened vintage component with its original package and foldout documentation, eliminating the guesswork of uninspected surplus lots. Shipping is $8 flat rate, free once the order passes $28, and orders leave our Idaho warehouse the same or next business day.
There is nothing quite like cracking into untouched 1970s silicon to make an old display glow the way it was born to. Wire it up, light the segments, and let the counter run.
