A portable battery-powered communications device is configured to operate in a bidirectional communications mode in which voice and/or data is communicated in a bidirectional manner using a bi-directional communications protocol; and to operate in an emergency beacon mode. When the device is in the emergency beacon mode the device is configured periodically to transmit an emergency positioning message at maximum power using the bi-directional communications protocol, transmission of the emergency positioning message defining a beacon transmit period; optionally, to listen for transmissions using the bi-directional communications protocol in a beacon response period immediately following the beacon transmit period; and to refrain from powering transmit and receive circuitry of the device other than during the beacon transmit period and the beacon response period.