Dial up usinng Asyn interface

[Tan Choh oon]

Hi,   I had 2501 router, 1 Ethernet , 2 Syn port and 1 Aux port. I like to coonect the 56k dial up modem to serial 0 , and configure it to DDR to ISP. My question is how do i configure the serial 0 ( syn interface)  to dial out ?   As far as i knew only asyn serial, Aux port and syn/async serial is capable to do dial up. Can Sync serial port do dial out ?? If can please give sample config.   Thanks.   C.K.Tan