Note that although both forms for expressing the line length are indicated as optional, one of the two must be specified. Note that this element models only one propagating mode. If all four nodes are distinct in the actual circuit, then two modes may be excited. To simulate such a situation, two transmission line elements are required. Current flow is from the positive node, through the source, to the negative node.
Current flow is from the positive node, through the source, to the negative node.
VNAM is the name of a voltage source through which the controlling current flows. VNAM is the name of a voltage source through which the controlling current flows. Note that voltage sources need not be grounded. Positive current is assumed to flow from the positive node, through the source, to the negative node. They will of course, have no effect on circuit operation since they represent short-circuits.