The Vista 20P (and all other Honeywell Control Panels) have a built-in phone dialer that sends alarm signals to your central monitoring station. Your central monitoring operator will then contact your home and dispatch police to your residence if necessary.
It is possible to equip your Vista 20P with a voice dialer, which automatically calls a series of pre-programmed home and cellular phone numbers with an automated message alert whenever an alarm is triggered. For those with self-monitored systems, the Eyez-On Envisa Link 3 IP module can be installed, which not only sends text and email alerts regarding system events and alarms, but gives users remote control of arming/disarming their security system from any mobile smartphone or internet device.