.CKT file extension

This is the basic program to work with .CKT extension

DXP 2004

DXP 2004 Advanced Sim Sub-Circuit

.CKT extension is also supported by the following programs:

Altium Designer

Altium Designer Simulation Sub-Circuit

Leverages innovative technologies to help you focus less on the process.
Altium Designer Summer 08

Altium Designer Summer 08 Simulation Sub-Circuit

Lets you create your next-generation of electronic products.
DXP 2004 SP2

DXP 2004 SP2 Advanced Sim Sub-Circuit

B2 Spice A_D Lite

B2 Spice A_D Lite Worksh Document

Ansoft Designer

Ansoft Designer HarmonicaProduct Class

Ansoft Designer is an integrated schematic and design management front-end.
Kubotek KeyCreator

Kubotek KeyCreator KeyCreator Template File

Crocodile Physics

Crocodile Physics

Crocodile Physics 605 1.0.0605 is a simulator that builds physics models.
Altium Designer Winter 09

Altium Designer Winter 09 Simulation Sub-Circuit