Electrical elements always have connections like wires, solder points, screw connections, plugs, contacts, pins etc., at which these are connected with other elements. The connection takes place via soldering, twisting wires, screwing together, putting, switching or other possibilities. During integrated circuits the connections are manufactured equal with the elements.
An individual connection (furthermore called pin) makes the connection of the electrical element to its environment. It takes place via the physical dimensions current and voltage. A pin has a voltage, which represents the difference of the electrical potential between the pin and a once specified point of reference. At the pin an electric current flows into the element, whose direction into the element is defined as positive:
As soon as two or several pins are connected, an electrical node has been developed, at which the Kirchhoff laws apply. That means the voltages of all pins at the node are the same, and the sum of the current of all pins at the node is zero.
For an electrical node the model object "electrical connection" was introduced, whose result value "voltage" is the voltage, which all attached pins carry. Since the currents per attached pin are different, they are not indicated with the connection, but with the pins of the respective electrical elements to be found.
To each electrical connection an initial voltage can be assigned. The initial voltages are treated like initial values by differential equations. The initial values assigned by the user do not have to fit necessarily (inconsistently). However, the simulator needs a consistent starting solution. Therefore it can occur that the initial voltages are changed with the first calculation step of the simulator.