Connection structures of modular assembly system

A connection structure, comprising:

• two connection interfaces, each connection interface comprising:
• a plurality of contacts arranged on a circuit board, and
• a plurality of first lock mechanisms arranged on a first casing;
• and
• a connector comprising:
• a second casing comprising two open ends and a plurality of second lock mechanisms arranged on the second casing, and
• a plurality of concentric ring contacts, each concentric ring contact comprising two ends each exposed by one of the two open ends of the second casing, respectively,
• wherein when the connector is plugged into the two connection interfaces at a plurality of orientations relative to one another,
• the plurality of concentric ring contacts of the connector are in contact with the plurality of contacts of each connection interface so that the two connection interfaces are electrically connected, and
• the plurality of second lock mechanisms of the connector are interlocked with the plurality of first lock mechanisms of each connection interface so that the two connection interfaces are mechanically connected.