3. The communications system according to claim 2 , wherein a respective telephone number for the first and second receivers of data strings is stored in the control and is updated when a configuration message is received.
3. The communications system according to claim 2 , wherein a respective telephone number for the first and second receivers of data strings is stored in the control and is updated when a configuration message is received. 5. The communications system according to claim 3 , wherein the second receiver of a data string is configured to send an acknowledgement of receipt of the data string.