A connection system includes a first connection module and a second connection module, which each have a first connection devices, the first connection module including a second connection device and the second connection module including a third connection device. There is a direct electrical connection between the first connection device of the connection module and the accommodated device and a direct mechanical connection between the connection module and the accommodated device. The first connection module can be locked directly to the third connection device such that the first connection module is electrically and mechanically connected to the second connection module. The third connection device is arranged such that, when the second connection device is locked to the third connection device, mechanical and electrical disconnection of the first connection module from the second connection module is prevented if the second connection module has received a device.