636 VOICE-BANDWIDTH VISUAL COMMUNICATION THROUGH LOGMAPS: THE TELECORTEX R. Wallace, B. Bederson, E. Schwartz, May 1993 We present a robotic video telephone application of the Cortex-1 miniaturized space-variant active vision system. The embedded processor architecture of Cortex-1 enables it to implement a variety of functions not found in conventional video telephones, for example the camera tracks moving users with its pantilt mechanism. We also report an analog channel coding scheme to transmit logmap video images through band-limited analog channels such as the public switched telephone network (PSTN). The transmitter divides the voice frequency band into 768 channels, and modulates two values in quadrature on each channel. Some channels are reserved for special calibration signals enabling the receiver to recover both the phase and magnitude of the transmitted signal. The remaining channels carry pixel intensities. We synthesize the signal in the frequency domain and run the FFT algorithm to implement a fast conversion to a real, time-domain signal. A phase-lock loop keeps the receiver frame-synchronized with the transmitter. We constructed an experimental video telephone that sends 1376 pixel logmap images at 3.9 frames per second through the PSTN. Using the analog channel coding scheme, we achieve an effective data transfer rate in excess of 40000 bits per second.