01 · Custom is a range, not a checkbox
Every quote says custom. The useful question is where on the range it sits: a configuration chosen at order time, a BOM variant on the same revision, or a new board that has to be designed, sampled and certified.
This checklist is built from the customization surface that appears on GEOLiNK spec sheets: CPU matrices on one PCB revision, BOM-selectable serial modes, selectable power inputs, optional TPM and PoE. Every example is an option that exists today, so you can calibrate any supplier's offer against it.
Field note
The sample is the specification. Ask that it carries the final CPU, the final serial mode and the final power option, not the closest stock unit. A sample that proves nothing about your configuration costs a quarter and a field trip.
02 · Four questions about the board
Start with what the board is, not what the price is.
Is the CPU a configuration option on this board, or a different board?
The answer separates one design with options from a family of near-identical designs. The UT1003AW lists twelve Core Ultra SKUs (135H through 255H) on one 3.5-inch revision, the AD742A offers N100, N305 and N150, and the TL500Z3AW covers Celeron 6305U to Core i7-1165G7. Ask for the CPU matrix on the same PCB revision. If each CPU needs its own revision, your spares and qualification multiply.
Which changes are BOM or order-time choices, and which need a new revision?
BOM options are cheap; layout changes are projects. The PNM-5210 configures three RS232 plus two RS485 by BOM, the ITX660B offers DC 12–24 V and 12 V power specifications at order time, and the TOP800B switches COM1 and COM2 between RS232 and RS485. Ask the supplier to sort every requested change into the two buckets before the quote.
What exactly changes in the BIOS, and who does it?
Industrial BIOS work is more than a boot logo: serial mode selection (the UT1003AW switches COM1 and COM2 to RS232, RS485 or RS422 in BIOS), watchdog defaults (the TOP800B spans 0–255 s, the FTEQ20A 255 levels), power-on behaviour (the HK800CA defaults to AT by jumper) and out-of-band management on the i226-LM or I219. Ask who owns the image, how long a change takes and whether it stays inside the standard firmware support window.
What is documented about my exact configuration?
Sheets carry revisions for a reason: the AD742A is R102, the UT100NU R101, the UT1003AW R100, the FTEQ20A R110 and the HK800CA R111. Ask whether the datasheet in front of you describes your CPU, memory, serial modes and power option, or the base board. A supplier that documents the configured variant saves you the audit later.
03 · Four questions about what happens after the PO
Configuration is the easy half. These four decide whether the product survives its own lifecycle.
What does a sample round look like, and what is the MOQ for a custom build?
Sample MOQ of one piece is the norm and the GEOLiNK default, but plan for one to three units on a custom build: one on the bench, one in the enclosure, one in transit. Standard samples leave in 2–5 days, production runs in 7–30 days, payment by T/T with L/C for larger orders, FOB Shenzhen.
How is the environment qualification proven for a custom configuration?
A custom SKU inherits the base qualification only if the parts changed do not shift it. The base numbers are −20/+60°C operating and −40/+85°C storage on wide-temp models, with input classes from DC 9–36 V down to 12 V. A different CPU or power stage should be re-validated rather than assumed. Ask what testing the configured variant goes through, and note that CE, FCC and RoHS documents are provided per project on request.
How is long-term supply handled, and what happens at component EOL?
Medical devices can spend one to three years in certification before the first unit ships, so the board must be orderable years after launch. Ask what the supplier does when a CPU or PHY reaches end of life: a substitute CPU on the same revision, a documented migration, or a forced redesign. The answer belongs in the contract, not the sales call.
Who owns the design change, and how are revisions tracked?
Confirm who holds the design files, who signs off a change that affects the electrical or thermal design, and how the revision number reaches the silkscreen, the datasheet and the firmware. That discipline decides whether fielded units are traceable when a batch-level anomaly appears. A supplier who hesitates here is a supplier you will argue with later.
