# Choose a transmission-line model before importing external network data

The maintained syntax documents explicit line models with different assumptions. Match the physical model and data format before planning a simulator handoff.

## Compatibility

2.9.0 release target; review-build/source evidence

Published guidance with release-applicability limits. Confirm package applicability before following this guide.

## Start with the supported representation

The current source reference lists LOSSLESS, LCLADDER, RLGC, WIDEBAND and MODAL line models, and an @MTL model with explicit constant RLGC matrices and a reference conductor.

These interfaces have distinct parameter, passivity and analysis constraints. For example, constant scalar RLGC is not a geometric field solver or a general frequency-dependent coupled-network import.

## Do not assume a file conversion exists

An older support discussion about arbitrary S-parameter black boxes does not prove a current import feature. The documented explicit line models likewise do not establish that an arbitrary Touchstone file can be loaded directly.

Before promising an InductEx-to-JoSIM handoff, identify the exact model, supported data form, frequency range and reference convention. Validate any fitting or reduction method separately.

## Sources and verification details

Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.



- support:SUP-016: Generalised editorial finding; outcome qualification retained
- josim-pro:docs/manual_source/sections/syntax.tex: Transmission-line model reference and limitations
- owner:technical-review-20261102: JoSIM-Pro 2.9 chosen as the public starting path; release availability must be checked before publication

- Arbitrary external-network import and any conversion workflow need explicit current capability evidence and a worked example.
- Support history informed this draft. Current-source guidance has been checked; a fresh walkthrough on the intended distributed release and product-owner review remain pending.

## Related guides

- [Variable-step mode rejects a transmission line](/knowledge-base/josim-variable-step-lines)