Signaling and control via call and SMS

A call-and-SMS communicator notifies up to 4 phone numbers by call or SMS when a contact input activates, and lets authorized numbers switch a relay output just by calling in and being recognized by caller ID, at no cost to the caller. SS21-4G, SC-VoLTE M2, and SC-VoLTE M3 run this signaling over 4G VoLTE instead of legacy GSM/GPRS or a physical PSTN line.

GSM/GPRS communicators
SS21-4G
GSM/GPRS communicators
SC-VoLTE M3
GSM/GPRS communicators
SC-VoLTE M2

What is a call-and-SMS alarm communicator?

It's a small module wired to an alarm panel or a dry contact that reports events by placing a phone call or sending an SMS to a preset list of numbers — no monitoring station, app, or internet connection required, just a SIM card and mobile coverage.

How does caller-ID relay control work without an app?

A caller dials the communicator's SIM number; the device recognizes the incoming caller ID against its authorized list, switches the relay, and disconnects the call before it's answered — so the call is free and no app, PIN, or SMS command is needed. SS21-4G supports up to 8 authorized numbers this way.

Which device replaces an analogue phone line?

SC-VoLTE M3 — 4G voice gateway with 2G fallback, handles incoming and outgoing calls for a PBX, analogue handset, or alarm panel dialler.
SC-VoLTE M2 — in transparent mode, emulates a landline for equipment needing a phone-line connection; in standalone mode, sends Contact ID-based SMS/call alerts instead.

Frequently Asked Questions

Do I need a smartphone app to use SS21-4G's relay control?

No — up to 8 phone numbers can switch the relay just by calling in; caller ID does the authentication.

Can SC-VoLTE M2 replace a landline for an alarm panel?

Yes — in transparent mode it emulates a TIP/RING landline connection over 4G VoLTE for equipment that expects a physical phone line.

What's the difference between SC-VoLTE M2 and SC-VoLTE M3?

M2 is built around alarm-panel signaling — Contact ID SMS/call alerts, plus optional landline emulation. M3 is a dedicated 4G voice gateway for analogue phone equipment, PBX systems, and diallers that need full incoming and outgoing calling.