Abstract: Accessory for a laptop computer with LCD display which is connected to the laptop serial communications port and optically transmits data to a portable information device, such as a wristwatch designed to receive data as sequential pulses of light. The accessory includes a microcomputer with an RC timebase which is calibrated each time it is used by a special internal program, so that the input baud rate to the accessory matches the communications baud rate of the data received from the laptop. The internal program also permits selection of an output baud rate for the optically transmitted data.