A card reader usually forces a choice: read the card, or keep the device charged. A magnetic dual-card reader with PD pass-through is designed to remove that choice. It attaches to the back of a compatible smartphone, exposes a TF slot and a full-size SD slot, and passes power straight through to the host while a transfer runs, so an offload can continue while the battery keeps filling.
Shenzhen LingC Industrial Co., Ltd. is a storage and computer-peripheral manufacturer based in Shenzhen, China. Its card reader line covers single-slot, dual-slot and multi-card designs, and the RD3012 carries this charge-and-read form factor. The model is in development rather than shipping, so this article is a pre-research exercise: what the form factor is worth, and which specification points a buyer should pin down.
What “Charge and Read” Actually Solves
On a shoot day the workflow is a loop: capture, offload, keep shooting. A phone recording high-bitrate video while moving footage off a card is doing two power-hungry jobs on one battery. If the reader occupies the only port, the only way to top up is to stop the transfer. That is the inconvenience a pass-through design targets — the host port carries data and power at once.
The same logic applies away from the camera. A field engineer, a sales team reviewing footage on a tablet, or a traveller backing up cards in a hotel room is usually short of both ports and outlets. A reader that carries 100W of pass-through power means one cable at the desk instead of a reader plus a separate charger.
The Specification Set Behind the Form Factor
| Specification | RD3012 |
|---|---|
| Status | In development |
| Host interface | USB-C 3.0 |
| Card slots | TF + SD, simultaneous dual read |
| Protocol | SD 3.0 DDR225, up to 200MB/s |
| PD pass-through | Up to 100W |
| Enclosure | Aluminium alloy, 58 × 58 × 10.1 mm, 40 g |
| Colours | Silver, black |
| Accessories | Right-angle USB-C flat cable, USB-A-to-C adapter, magnetic ring |
| Operating temperature | 0 °C to 70 °C |
| Warranty | 3 years (card reader line) |
Two details matter more than the rest. The first is the slot pair: the sheet specifies TF and full-size SD with simultaneous dual read, so a creator can move a camera card and a TF card without swapping anything. The second is the mounting kit — a magnetic ring lets the reader sit flat against a phone that has no magnetic back of its own, which is what makes the assembly usable one-handed.
Four Points Buyers Should Verify Before Ordering
1. Slot types and whether they read at once
TF and full-size SD are different mechanical formats, and some dual-slot designs switch between them internally rather than reading both at once. Confirm the simultaneous-read behaviour on the sample: a switching reader is a different product to the end user even when the port count looks identical on paper.
2. PD power tiers and pass-through behaviour
PD pass-through is a negotiated budget, not a fixed claim. Ask what the ceiling is, what happens to the data link when the host negotiates a lower wattage, and whether the fast bus needs external power. The model sheet lists up to 100W; the practical figure depends on the charger and the tier the host accepts, so quote the ceiling and the tested conditions together.
3. Magnetic fixing and cable routing
A magnetic reader is only useful if it stays put while a cable is connected. Verify magnet strength against the phone weight, whether a ring is included for phones without a magnetic back, and how a right-angle connector keeps the assembly flat. A straight connector forces the cable into a loop that catches on pockets, tripods and gimbals.
4. Compatibility and host behaviour
Confirm which host operating systems the reader enumerates on without a driver, that both slots appear as mountable volumes, and that the supplied cable can carry the reader’s bus class. Cards, host ports and cables each cap throughput independently, so a fast card on a slow cable still transfers slowly.
Where the Form Factor Earns Its Place
- Phone-led creators — offload footage during a shoot without pausing to charge.
- Camera-to-phone handoff — move a camera SD card and a second device’s TF card in one pass.
- Mobile office and travel — one connection for cards and power on a port-poor laptop or tablet.
Pre-Research Status and Next Steps
Because the RD3012 is in development, treat everything above as a specification target rather than a shipping datasheet. Certification for this specific model can be arranged upon order confirmation. MOQ and lead time are quoted per configuration — model, packaging and customization depth — with the schedule confirmed in the quotation after sample approval. Where the model sheet lists two different figures for the same accessory cable, confirm the final length against the sample before packaging artwork is printed.
Frequently Asked Questions
Can a reader charge the host and read a card at the same time?
That is the purpose of PD pass-through: the host port carries data and power together, so a transfer does not stop for charging. The ceiling depends on the charger and the PD tier the host accepts.
Can the reader work on a phone without a magnetic back?
Yes — the kit includes a magnetic ring, which provides an attachment surface for phones that have none built in.
Is the RD3012 available to order now?
It is an in-development model. Buyers who want it in a range should contact the sales team to discuss status and a customized configuration.
Summary
A magnetic dual-card reader with PD pass-through exists to remove a sequencing problem: read the card, or charge the phone. Specifying one means confirming four things — that the TF and SD slots read simultaneously, what PD tier the pass-through supports, how the magnet and cable keep the assembly flat, and which hosts enumerate both cards without a driver. LingC builds card readers, hubs, flash drives, TF cards and SSDs from a single Shenzhen site; see the full card reader range or review the RD3012 specifications.