EV3 and NXT: Difference and Compatibility http://robotsquare.com/2013/07/16/ev3-nxt-compatibility/
The cable connectors in the NXT sets and EV3 sets are the same, so that many of the EV3 and NXT devices can be used together. Some combinations are compatible, others are not, as discussed in the next. You can see a demonstration of two possible configurations in the following video.
You can connect all official LEGO NXT motors and official LEGO NXT sensors to the EV3 brick. For example, you can have a configuration with an NXT Touch Sensor, an EV3 Touch Sensor, an NXT motor and a Medium EV3 motor, all connected to the EV3 brick, as shown in Figure 4. You use the NXT devices in the EV3 software as if they are EV3 components, as demonstrated in the video.