what is a self-contained power hammer？

Anyang ST power hammer for blacksmthing forging is a self-contained design hammer, The self-contained power hammer works by two cylinders, the back cylinder make compressing air, and the front cylinder run the ram hitting and lifting. The motor drive the piston in the back cylinder via the rod to make compressed air go to the front cylinder through the valves that control the stroke displacement.

Anyang ST power hammers with below advantages:
Built-in compressor.
Maximum drop precision, controlled via a next-generation valve.
The casting frame is solid and strong.
Automatic greasing system.
Intake and exhaust mufflers.
No need for civil engineering work or special foundations for installation.
Inner tray to collect greasing oil.
Near-zero maintenance.
Double mechanical stop protection.
Height and orientation adjustable protection on the front.
Drive system pedal protection.
Electric engine protection.
Emergency stop.
CE marking.