What changes can be made to the TSA-a/b in the event of insufficient volume in the loudspeaker of Siedle door intercoms?

Many Siedle call stations can be rewired internally so that the loudspeaker is led out at terminals 12 and 13 (without the built-in transistor amplifier). Connect terminal 12 of the Siedle module to one of the door intercom contacts (make contacts 1/2 on the TSA-a/b), connect the other door intercom contact to terminal LSP of the TSA-a/b. Connect terminal 13 of the Siedle module to the 0V contact on the TSA-a/b. This results in a greater maximum volume.