Some systems are capable of transmitting more details than others. For example: those systems with a built-in dialer are capable of transmitting CID (contact ID) which in other words mean that each device can send signals to central station. Then if you have 200 smokes, each sends over its own name and location over to CS. this is known as built in dialer. On the other hand, a communicator has only between 5 to 10 zones and send a generic signal such as trouble, supervisory, alarm, phone line troubles etc but lacks the ability to send one signal per field device