hi
In case of normal ISDN dial outs you have the option of defining dialer-list and dialer groups which basically works together to trigger the isdn line when they see any interesting traffic.
Interesting traffic can be defined using the ACLs and binded with the dialer-list command.
About idle time outs you can very well refer dialer idle-timeout and dialer fast idle commands to achieve that.
do check these links for more info on the same..
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hdia_r/dia_d1h.htm#wp1179390
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hdia_r/dia_d1h.htm#wp1179127
Can you post out the config you have in place at your soho97 router ?
regds