Normally the S-Bahn Hamburg drives trains of the serie 474. They takes their traction (1200V DC) on an extra rail, beside the track. On line S3 (Pinneberg-Hamburg-Stade) the S-Bahn is driving in the section Hamburg-Stade under the catenary. For this line (S3) an adapted serie of the 474 has been build with extra pantograph and named 474-3. On this section there is no extra traction rail. This section of the line S3 is the normal railway Hamburg - Stade - Cuxhaven. Only the part Hamburg - Stade is under catenary and driving by the S-Bahn. From Stade to Cuxhaven the trains are driving by the METRONOM company with diesel locomotives Bombardier Trax.
On line S3 (Pinneberg-Hamburg-Stade) the S-Bahn is driving in the section Hamburg-Stade under the catenary. For this line (S3) an adapted serie of the 474 has been build with extra pantograph and named 474-3. On this section there is no extra traction rail. This section of the line S3 is the normal railway Hamburg - Stade - Cuxhaven. Only the part Hamburg - Stade is under catenary and driving by the S-Bahn. From Stade to Cuxhaven the trains are driving by the METRONOM company with diesel locomotives Bombardier Trax.
https://de.wikipedia.org/wiki/DB-Baureihe_474