Only one B201 is allowed on the B3512, B4512, B5512 or B6512. This module draws 35ma when in alarm. The B201 is designed to use an Open Collector output and open collector outputs can sink up to 50 mA. An additional current draw of a second B201 would exceed the maximum current draw allowed. Therefore only one B201 is allowed on B-panels.
Use the D125B when more than one 2-wire loop is required. See the B-Panel installation module for configuration instructions.