Key Takeaways
- Scenario 520 is early dismissal on a heat-index or air-quality day: one 10:30 parent blast. Campus office SIM dies under the spike — a spare already paired takes the rest. Not a Sunday LMS, sub-teacher OTP, or exam failover.
- Parents who get silence will call the front desk. The product is the second radio, not a prettier dashboard.
- Do not SMS student names or bus-stop maps in message 1. Time, pickup rule, and a short URL if you must.
- Staff portal OTP stays on another device.
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free: 1 device / 300 SMS lifetime / 300 contacts. Developer: 25,000 SMS per year.
Android SMS gateway scenario 520 is a district office on a red heat-index morning. Dismissal is 11:15. The parent list is thousands. The front-office SIM will throttle. Period-bell join codes and lottery failover are the wrong list.
Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Failover · Developer Center. GSMA.
Dismissal, not a join code
Split the parent list across two device ids before send. Fail closed if both SIMs report carrier reject.
If you discover the spare in a drawer after the first thousand fail, you ran a press conference, not a dismissal.
Heat-index vs LMS
| Lane | Body | Failover | Device |
|---|---|---|---|
| Early out | Time, pickup rule | Split list | Office + spare |
| LMS join / exam | Code | Class modem | Separate |
| Staff portal OTP | Digits | Auth | Dedicated |
Caps: 2 / 5 / 15.
Spare already paired
Health-check both radios at 09:00 on watch days. REST: PHP, C#. MCP wraps REST.
No student names
Pickup rule only. Identity on inbound if they reply WHICH GATE.
Devices and airtime
Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free: 300 lifetime. Developer: 25,000 SMS per year. Pricing.
10:30 blast
Campus SIMs
Log campaign id + device id, not the student roster in chat. Rotate keys. Not a CodeCanyon district pack.
Two SIMs or silence
If you will not keep a hot spare on heat-watch days, do not promise SMS dismissal.
Checklist
- Spare paired night before.
- List split before send.
- No names in templates.
- Staff OTP elsewhere.
- Webhook signatures.
Next steps
Kill the office SIM mid-test list; prove the spare finishes the remainder. Downloads · Docs.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- multi-device and dual SIM routingCapacity and failover
- OTP and 2FA SMS on AndroidAuthentication flows
- SMS delivery reports (DLR)Delivery status tracking
- SMS API documentationLive endpoint reference
