Abstract: A network device, configured with common and emergency call resources for connecting a telephone terminal to a local exchange, includes a storage module, a control module, and a digital signal processor. The storage module stores a plurality of emergency call numbers. The control module detects a public switched telephone network (PSTN) dialing signal from the telephone terminal and determines if the common call resource has been exhausted upon detecting the PSTN dialing signal. The digital signal processor receives a PSTN call number from the telephone terminal upon the condition that the common call resource has been exhausted, determines if the PSTN call number matches with one of the emergency call numbers, and redials the PSTN call number to the local exchange via the emergency call resource upon the condition that the PSTN call number matches with one of the emergency call numbers.