The ultra-small 4P-AGW (4-port type) provides a four-subscriber port for general PSTN phone or public phone service, can use an EPON or UTP (Ethernet) interface for interworking with call processing devices, and includes batteries in the equipment for uninterrupted service. For ease of space utilization, the ultra-small 4P-AGW can be used to minimize the upper surface through SLIM of the equipment and lightening of the equipment, and it also has the advantage of not having to use separate space by installing the battery in the equipment.