Product Overview
Archer 276-225 Fiber Optic Emitter and Detector Set, Unused on the Original Card
Condition
Unused, new-old-stock. The pair is still in its clear factory pouch on the original Archer card, printed Cat. No. 276-225, $4.99, and CUSTOM PACKAGED IN USA BY RADIO SHACK, A Division of Tandy Corporation, Ft. Worth, Texas 76102. Through the plastic, both devices show clean black knurled cable clamping nuts, flanged mounting feet with an open mounting hole, and two straight leads each with no solder anywhere on them. One body carries the Motorola M logo and reads MFOD72 8552 KOREA, and that device's mounting flange is bright bare metal; the second device photographs as a matte light gray body and foot, lying marking-side down in the pouch, so its part number is not legible in any of the photos. The card shows its age: soiled edges, creasing across the lower panel, and a split in the card stock below the bubble. The folded Archer Technical Data Sheet for catalog number 276-225 is included, yellowed and creased along its original folds, complete and fully legible. One set in stock.
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Product Overview
The Archer 276-225 is a matched infrared emitter and detector pair that Radio Shack sold to experimenters as a complete short-haul fiber optic data link: the Motorola MFOE71 infrared emitting diode on the transmit end and the MFOD72 infrared detector diode on the receive end. Both devices are built as connectorized packages rather than bare diodes, with an internal molded lens, a flanged mounting foot for panel or chassis mounting, and a knurled clamping nut that captures the fiber. According to the included Archer technical data sheet, the connectors terminate directly to low-loss 1000 micron plastic fiber optic cable, with Archer Cat. No. 276-228 named as the matching cable, and the sheet gives 820 nm peak wavelength for the emitter and 125 uA/uW responsivity for the detector. The same sheet prints the pin assignments, the fiber preparation procedure, and demonstration circuits for TTL transmit and receive, a digital to analog converter, and a small signal amplifier. This is the carded 276-225 set with that sheet, sold as a unit.
Key Features
- Set contents: one MFOE71 infrared emitting diode and one MFOD72 infrared detector diode
- Device marking observed in the photos: Motorola M logo with MFOD72 8552 KOREA on the one device that lies marking-side up; the second device's marked face is not shown, and the MFOE71 designation comes from the card and data sheet rather than from a photographed marking
- Fiber: terminates to low-loss 1000 micron plastic fiber optic cable per the included data sheet, which names Archer Cat. No. 276-228 as the matching cable
- MFOE71 typical peak wavelength: 820 nm at 100 mA (data sheet)
- MFOE71 typical power launched: 165 uW, optical rise and fall time 25 ns (data sheet)
- MFOE71 maximum ratings: 6.0 V reverse voltage, 150 mA forward current, 2.0 V forward voltage, 150 mW power dissipation (data sheet)
- MFOD72 maximum ratings: 30 V collector-emitter voltage, 150 mW power dissipation, 100 nA collector dark current, 0.4 V saturation voltage (data sheet)
- MFOD72 typical characteristics: 125 uA/uW responsivity at 5 V, 10 us turn-on time, 60 us turn-off time (data sheet)
- Pin assignment per the sheet: E71 pin 1 anode, pin 2 cathode; D72 pin 1 emitter, pin 2 collector
- Mechanical: integrated molded lens assembly, knurled cable clamping nut, flanged mounting foot with mounting hole
- Packaging: original Archer blister card, Cat. No. 276-225, with the folded technical data sheet included
Applications
- Restorer rebuilding a 1980s Radio Shack fiber optics experiment who needs the original 276-225 devices rather than a modern substitute
- Electronics instructor running an optical data link demonstration over plastic fiber using the TTL transmitter and receiver circuits printed on the included sheet
- Hobbyist building the lightwave voice transmitter and receiver the sheet points to in Getting Started in Electronics, Cat. No. 276-5003, substituting MFOE71 for the infrared LED and MFOD72 for the phototransistor
- Bench engineer who wants a short isolated logic link over plastic fiber, with a connectorized emitter and detector already sized for 1000 micron cable
- Tandy and Radio Shack collector after a complete carded Archer example with its data sheet intact
Frequently Asked Questions
What exactly comes with this set?
One MFOE71 emitter and one MFOD72 detector on the original Archer 276-225 card, plus the folded Archer technical data sheet shown in the photos. Fiber optic cable is not included. The sheet names Archer Cat. No. 276-228 low-loss 1000 micron plastic fiber as the matching cable.
Has the pair been tested or powered up?
No. It is sold as unused new-old-stock in its original packaging and has not been powered, measured, or removed for evaluation. Every rating above is quoted from the included Radio Shack data sheet, so verify against that sheet before you design around it.
How is the fiber prepared and attached?
The included sheet gives the procedure: strip the cladding back about 1/2 inch to expose the bare core, scribe the core around its circumference, and break it off so 0.100 to 0.180 inch of core extends past the jacket. Loosen the clamping nut, slip the fiber through until the core tip seats against the internal molded lens, then snug the nut without overtightening.
Will you open the package before shipping?
No. It ships exactly as photographed, devices on the card in their factory pouch with the data sheet alongside.
Why buy one carded set here instead of a bulk lot of optoelectronics elsewhere?
Because a 276-225 restoration or a single classroom demo needs one set, not ten. PartsMine sells the exact quantity you need, one or two pieces for a repair or a prototype, instead of forcing a lot of 10 or 50. Shipping is $8 flat rate and free over $28, and orders leave our Idaho warehouse the same or next business day.
For $4.99 on a peg hook, Radio Shack handed the experimenter a working light-speed data link and a folded sheet of schematics to prove it. This pair never made it to a breadboard, so the fiber, and the circuit at the far end of it, are yours to pick.
