Abstract: A telecommunications system having at least one base unit and a plurality of portable units is arranged to enable automatic re-registration of a portable unit with the system. The portable unit includes system and unit identity detectors and a registration sequence generator. The registration sequence generator is connected to a timer which monitors the elapse of time since a signal from a base unit of the system intended for the portable unit is received. The registration sequence generator generates a re-registration request in the event the monitored elapse of time is greater than a predetermined period and a signal from a base unit of the system is received which is not intended for the portable unit. With the system described portable units can automatically re-register with the system after being out of range of a base unit without the need for a separate beacon signal.