Operating on the Repeater
To access a System Fusion repeater, you only need to know the frequency, offset, and tone. What?! Why do you need a tone?
"System Fusion" actually refers to the ability of Yaesu radios and repeaters to automatically switch between analog FM and digital C4FM (the "Fusion" of C4FM and analog). The official Yaesu term for this is "Automatic Mode Select." If you have a repeater dialed in and AMS enabled on your radio, you will hear both analog and digital traffic. When you press the PTT, your radio will transmit is what ever mode it last heard. It should now be obvious why you need to know the repeater tone, otherwise your analog traffic would not make it into the repeater.
If you already have one of Yaesu's Fusion radios and already have the repeater programmed in your memories, the only thing you need to do is select your mode. This varies slightly from radio to radio. On the FTM-400, short press of the red "DX" cycles through the available modes. On the FT2D, the "Mode" button in the bottom-right corner of the touch screen cycles through the modes. A horizontal line above either DN, VW, or FM indicates that Automatic Mode Select is enabled.
The best practice would be to start with AMS enabled. If a QSO is not in progress, switch to whatever mode you like for your transmission. Note that only digital transmissions go out over the WIRES-X network. For this reason, if you intend to operate on WIRES-X, you radio should be set to Digital-Narrow.
Another alternative that many use is to have two different channels saved for the repeater; one digital and one analogue. In this configuration, switching between digital and analogue is as simple as switching channels.
If you do not have a Yasesu radio capable of Fusion, you can still use the repeater. If have not done so already, the first thing you will want to do is to select tone-squelch. If you have tone-squelch enabled, you will hear all of the analog FM traffic on the repeater; but TSQL will keep you from hearing the roar of the digital traffic on your FM rig. Unfortunately, FM traffic on the repeater is local-only and does not go out over WIRES-X. DTMF tones to the repeater over FM will simply be ignored.
Important note: the repeater cannot cross-mode between FM and C4FM; it simply transmits in whatever mode it has received. This is why using AMS or the '2-channel' setup mentioned above is important during common operation.