0. Introduction, Change log, ToDo list

0.1 Introduction

CI-V stands for Computer Interface 5 and is ICOMs designation for their rig interface to a computer or to another rig. You can find it on most HF and some VHF rigs since the 1980s and is has not changed in it's basic structure up to now. CI-V is a simple to use interface which allows, in contrast to other manufacturers designs, a "daisy chaining" of rigs (see Principle of operation).

To connect just two rigs you need nothing more than a cable with two 3.5mm mini plugs. For a connection to a computer you need an additional interface for most rigs (see CI-V interfaces). Some rigs provide a RS-232 interface and do not require an interface, just a serial cable.

The protocol (what and how information is transmitted over the cable) is quite distinct from other manufacturers designs, allowing for many options, but is sometimes more difficult to use (for the programmer). This protocol has evolved over the past years, and more and more functions are now remote controllable. Older rigs support a basic set of functions, like setting and reading the frequency, mode etc. Newer rigs allow to remote control practically all functions the rig provides. See Which rig supports which command?.


Througout this documentation I use hexa-decimal notation for binary data. Such data is preceeded by the "$" symbol, as it is used in the Pascal language for hex constants. Other symbols are "0x" (in C, C++) or "&H" (in Basic). So $2F equals 0x2F equals &H2F (and is 47 in decimal notation).

Compatibility with the older Icom CI-IV system

The older version CI-IV is not compatible with CI-V. CI-IV was used at least in the venerable IC-751A and IC-R71. Icom used to offer a converter CI-IV to CI-V called UX-14, but this device is no longer available and very rare on fleamarkets or auctions. The US company Piexx offers a replacement for the UX-14 board.

What about other Icom rigs? Handhelds etc.

The CI-V system is used by all Icom amateur HF rigs since the IC-735, all desktop receivers since the IC-R7100 and with two handheld scanners (IC-R10, IC-R20). Other Icom products like handheld two-way radios, marine products, FM mobile rigs don't use the CI-V protocol and are not covered in this document.

I have looked briefly at the handheld Icom two-way radios, they seem to use a somewhat similiar protocol as CI-V, but incompatible. And usually these radios only allow 'cloning' with this protocol, i.e. copying memory contents from one rig to the other.

Someone told me that the Icom marine products are also remote controllable, but the protocol is entirely different from CI-V. I have no information about that protocol.

What about other manufacturers? (non Icom)

Of course other manufacturers radios are also remote controllable. But since I am an Icom fan since my youth (perhaps I inherited that trait from my father, DJ6XR (sk)) I first gathered most information about that manufacturers protocol. And thus I want to provide as complete information about this one protocol, not to be deterred by other products. This does not imply that other radios are bad or less perfect, but still I prefer Icom.

Why don't I publish this collection of information as a PDF file?

Because PDF files are static and this site is dynamic. I.e. it evolves, contents is added and changed from time to time. With a PDF copy you would never know if you have the most recent version on your disk or not.

0.2 Change log

0.3 ToDo List