It's now possible to directly drive up to 60 continuous amps on each channel of a dual-channel dc motor controller at up to 40 V. The microcomputer-based AX3500 provides optical-encoder input for automatic guided vehicles, underwater remotely operated vehicles, and mobile robots for exploration, hazardous material handling, and military and surveillance applications. The 4.2- by 6.75-in. device accepts commands from either a standard R/C radio or a serial-port interface that allows it to be connected to single-board computers, wireless modems, or wireless local-area network adapters in fully autonomous or semi-autonomous robots. It has inputs for two quadrature encoders up to 250 kHz and four limit switches. The two channels can be operated independently or combined for differential steering. The AX3500 is available for $395 in single quantities, complete with cable and PC-based configuration software.