Scout

The Scout is the blue MINDSTORMS brick from the Robotics Discovery Set (9735, 1999). The ~4×3" brick has an LCD screen, 4 buttons, 2 touch inputs, 2 motor outputs, a built-in light sensor, indicator LEDs, and 6 AA cells. It both reads light and emits VLL to command smaller bricks.

Optical input / output

• IR (input) — the Scout receives commands over IR: from the IR tower (driven by NQC / BricxCC) and from the LEGO Remote Control (handheld). This is its main remote / PC channel — RCX-class.
• Light sensor (input) — standalone triggers (light-change alarm / fire a dart) and sensing; per the VLL family it also decodes VLL codes (shared codebase with Micro Scout / Code Pilot).
• VLL emitter (output) — the Scout can transmit VLL (red LED / Motor C) to command a Micro Scout. One of LEGO's sanctioned ways to fill the Micro Scout's P slot (LEGO FAQ — P program & IR tower).

Programming & control

• Standalone: ~3000 command combinations selectable via the LCD + buttons (no PC needed).
• From a PC over the IR tower: NQC / BricxCC downloads programs and drives the Scout live (BricxCC's Direct Control panel = remote-style motor/sound commands). The Scout is an RCX-class target reached over IR via the tower (the serial 9713 plugs into a PC 9-pin serial port; USB 9783 also works — so "9-pin serial" is the tower's PC link, not a cable to the brick). Older path: the Scout SDK (ScoutTool.exe / ScoutDOS.exe, LASM) — pbrick.info / LEGO official docs — Tower Interface + Scout SDK.
• LEGO Remote Control (handheld IR, MindStorms line): drives the Scout directly — motors, run a stored program, beep.
• The SDK's vll opcode sends a 7-bit VLL command (canonical list: VLL opcode table).

Links

• Set: 9735 Robotics Discovery Set (1999) — see Sets & bricks index; Rebrickable.
• Part: 32104c01 (Rebrickable).
• Programmable in NQC (NQC explicitly targets RCX, CyberMaster and Scout) and in ROBOLAB (LabVIEW, education).