Cross-point matrix for infrared touchscreen

A circuit assembly detects a touch point within a display area. A plurality of light emitters are disposed around a periphery of the display area. A plurality of detectors are disposed around the periphery, each detector being opposed to a respective light emitter. Switching circuitry for connecting the light emitters and detectors in a switching matrix has a plurality of matrix rows and matrix columns. The switching circuitry includes a plurality of row lines, each row line corresponding to a respective matrix row and a plurality of column lines, each column line corresponding to a respective matrix column. Low-side switching transistors selectably couple the light emitters and detectors to the row and column lines, respectively. A common modulated signal is coupled to the anodes of all the light emitters. A detection signal is provided by connecting the collector terminals for the detector phototransistors in common. Consequently, high-side multiplexing circuits are avoided.