Sorry for the delay in replying.
Today has been the first time I have been able to get the 2404 on line.
Imperfect memory.

Firmware 3.18.1a4

With no ADSL connection the 'tick' LED blinks green slowly.

Connect the ADSL and the 'tick' LED blinks fast.

It then goes and stays solid green.

Very shortly after the '@' LED lights solid red.

After a delay it lights solid green.