`len`

This provides the physical length of the transmission line in arbitrary units, though the units must match the per-length unit in the element values discussed below. If not given, the value is taken as unity, unless it is implicitly defined by other parameters.`l`

This parameter provides the series inductance per unit length of the line. The default is 0.`c`

This parameter provides the shunt capacitance per unit length of the line. The default is 0.`r`

This parameter provides the series resistance per unit length of the line. The default is 0.`g`

This parameter provides the shunt conductance per unit length of the line. The default is 0. With level 2, this cannot be nonzero if`l`or`c`is given, i.e., only`r`can be nonzero if`g`is nonzero for level = 2, as in the SPICE3 LTRA model.`z0`or`zo`

This is the line (lossless) characteristic impedance in ohms, given by*Z*_{0}=`td`or`delay`

This is the (lossless) phase delay of the line in seconds, given by*T*_{d}=*Length*`nl`

This is the normalized line length at a particular frequency*f*, which must also be specified (see below). This is an alternative means for setting the line delay, where*T*_{d}=*nl*/*f**td*and*nl*.`f`

This is the frequency at which the normalized line length (above) is representative.

To model a line with nonzero series inductance and shunt capacitance,
a complete but non-conflicting subset of the parameters `l`, `c`, `z0`, `td`, `len`, `f`, and `nl` must be
provided. The `td` parameter is the line delay in seconds, and
the `z0` parameter is the impedance in ohms, for the lossless
case. Specifying these two parameters is sufficient to completely
specify a lossless line, or the reactive elements of a lossy line.
Alternatively, one could specify `l` (inductance per length), `c` (capacitance per length) and `len` (line length). If `len`
is not specified in either case, the length defaults to unity. The
delay can also be specified through the `f` (frequency) and `nl` (normalized length) parameters, where the delay would be set to
`nl/f`. It is an error to specify both `td` and `f`, `nl`. If `td` is specified, or both `f` and `nl` are
specified, along with parameters which yield internally the L and C
values, then the length is determined internally by

One can specify `z0` and `l`, for example, which determines C.
Unlike the SPICE3 (and SPICE2) lossless line devices, the delay must
be specified through the parameters; there is no default.