The eTiger S4-C-EU GSM/Phone alarm system has to be connected to your landline. Slot a SIM card into the main panel to receive an SMS message or a phone call. The starter kit consists of 2 motion detectors, 2 window/door sensors, 2 remote controls, and 2 RFID tags. You can expand the system to include up to 50 sensors. When a sensor detects a threat, it'll trigger a 100-decibel audio signal. Next, up to 5 preset phone numbers will be notified of the detected threat by means of an SMS message, a phone call, or a message in the app (iOS and Android). It's also possible to make phone calls straight from the control panel. You can easily switch the system on and off with the remote control, RFID tag, or the app.It's possible to slot a SIM card into the system, so that you'll also receive an SMS message in addition to a phone call when the alarm is triggered. This isn't necessary, though, and the SIM card isn't included by default.