If by "buy PLB" you mean a personal locator beacon (PLB) — a device that sends a 406 MHz distress signal to the COSPAS‑SARSAT/NOAA system — here’s a quick, practical guide to buying one and what to do after purchase.

1. What to look for (must-haves)

• 406 MHz (COSPAS‑SARSAT) with GPS/MEOSAR capability so your coordinates are sent. (sarsat.NOAA.gov)
• Long operational battery life and clear battery‑replacement/expiry info (most PLB batteries last several years and must be replaced before expiry). (Amazon.com)
• Waterproof/buoyant if you’ll be on water, and rugged for outdoor use. (Amazon.com)
• Return‑Link Service (RLS) if you want confirmation the distress signal was received (not all PLBs provide this). (Amazon.com)

2. Typical price range and example models

• Expect about $300–$600 for mainstream, MEOSAR/406 MHz PLBs. Examples: ACR ResQLink 400 (~$380) and ACR ResQLink AIS PLB‑450 (~$570); Ocean Signal rescueME PLB1 (~$395). Prices vary by model and seller. (Amazon.com)

3. If you want two‑way messaging (not just SOS)

• PLBs only send an SOS (one‑way). For two‑way text, tracking, and interactive SOS confirmation you should consider a satellite messenger (Garmin inReach family, etc.), which requires a subscription. Compare a PLB (one‑time buy, no subscription) vs an Iridium/Globalstar messenger (two‑way but has airtime fees). (Garmin.com)

4. Where to buy (safe options)

• Buy from the manufacturer or reputable retailers (manufacturer stores, Amazon, REI, West Marine, specialty marine/outdoor shops). Buying from authorized dealers ensures warranty and correct unit programming. Example product pages: ACR and Ocean Signal listings. (Amazon.com)

5. Mandatory post‑purchase steps (important)

• Register your PLB with NOAA’s National Beacon Registration Database right away (registration is required in the U.S.; it’s free and must be kept up to date and renewed every 2 years). Failure to register can result in penalties and slows rescue response. (beaconregistration.NOAA.gov)
• Read and follow the manufacturer’s test instructions — do not transmit a real distress signal when testing. (sarsat.NOAA.gov)
• Note battery replacement timelines and any service requirements; store/access the PLB where you can reach it quickly in an emergency. (Amazon.com)

6. Quick recommendation (if you want a short pick)

• If you want the simplest, subscription‑free emergency option: ACR ResQLink 400 or Ocean Signal rescueME PLB1 (both are widely used). If you want two‑way messaging + tracking: Garmin inReach (requires subscription). (Amazon.com)

If you meant something else by "PLB" (a stock ticker, token, or other product), tell me which one and I’ll give specific buying steps for that. If you want, I can also look up current prices/authorized sellers or show buy links for a specific PLB model and include step‑by‑step registration help.