System for treating flat pieces, in particular plastic cards, comprising a first module with a first treatment device; a second module with a second treatment device; an intermediate device for transferring a flat piece from the first module to the second module; and a control unit which is coupled to the first module, the second module and the intermediate device, characterised in that the intermediate device comprises: a receiving position and an output position; a buffering unit with at least a first and a second buffering position (22, 23, 24, 25); a first gate element, which is configured to hold the flat piece at the first buffering position, and a second gate element (22a, 23a, 24a, 25a), which is configured to hold the flat piece at the second buffering position (22, 23, 24, 25); and a control interface for receiving a control signal; wherein the device is configured such that, depending on the received control signal, the flat piece is received at the receiving position, held at the first buffering position, passed on to the second buffering position (22, 23, 24, 25) and held at the second buffering position (22, 23, 24, 25), and output at the output position; wherein the control unit is configured to, if an interruption state of the second module is detected, generate a first control signal such that the flat piece is held at a buffering position (21, 22, 23, 24, 25) of the intermediate device until a second control signal is received and the flat piece is output to the second module. a first module with a first treatment device; a second module with a second treatment device; an intermediate device for transferring a flat piece from the first module to the second module; and a control unit which is coupled to the first module, the second module and the intermediate device, characterised in that the intermediate device comprises: a receiving position and an output position; a buffering unit with at least a first and a second buffering position (22, 23, 24, 25); a first gate element, which is configured to hold the flat piece at the first buffering position, and a second gate element (22a, 23a, 24a, 25a), which is configured to hold the flat piece at the second buffering position (22, 23, 24, 25); and a control interface for receiving a control signal; wherein the device is configured such that, depending on the received control signal, the flat piece is received at the receiving position, held at the first buffering position, passed on to the second buffering position (22, 23, 24, 25) and held at the second buffering position (22, 23, 24, 25), and output at the output position; wherein the control unit is configured to, if an interruption state of the second module is detected, generate a first control signal such that the flat piece is held at a buffering position (21, 22, 23, 24, 25) of the intermediate device until a second control signal is received and the flat piece is output to the second module. a receiving position and an output position; a buffering unit with at least a first and a second buffering position (22, 23, 24, 25); a first gate element, which is configured to hold the flat piece at the first buffering position, and a second gate element (22a, 23a, 24a, 25a), which is configured to hold the flat piece at the second buffering position (22, 23, 24, 25); and a control interface for receiving a control signal; wherein the device is configured such that, depending on the received control signal, the flat piece is received at the receiving position, held at the first buffering position, passed on to the second buffering position (22, 23, 24, 25) and held at the second buffering position (22, 23, 24, 25), and output at the output position; wherein the control unit is configured to, if an interruption state of the second module is detected, generate a first control signal such that the flat piece is held at a buffering position (21, 22, 23, 24, 25) of the intermediate device until a second control signal is received and the flat piece is output to the second module.