only 4 wires?

Your new bell will not be operating as designed but.

1 core to hold off +
1 core to hold off -
1 core to trigger, linked to strobe
1 core as tamper return

You may have to link the strobe + to the hold off + As you have not mentioned the make of sounder.

This will mean the strobe will cut off with the bell timer (15 mins now the legal limit).

Alarm
August 2011