Abstract: A circuit is described for selectively increasing the number of text rows on the display screen of a CRT. The number of scan lines in each text row is reduced by one in response to a display format selection signal. The scan lines so saved are utilized to form two additional text rows. A variable modulus scan line counter is used in combination with a decoder to provide the scan line counter modulus desired. Additionally, a text row counter is used in combination with a second decoder to selectively change the modulus of the text row counter to correspond with the selected modulus of the scan line counter. A compressed display is provided by simultaneously changing the modulus of both the scan line and text row counters.

Abstract: Digital logic apparatus for demodulating a received phase-modulated carrier wave wherein phase-shifts between successive signalling intervals encode data elements. A shift register serially stores periodic samples of a squared version of the received wave. Exclusive-OR gates compare pairs of stored wave samples, each pair comprising a sample from a previous signalling interval and a sample from a current signalling interval. At least one of the exclusive-OR gates derives synchronizing signals for a local timing generator. For each data element, an integrator is associated with one of the exclusive-OR gates to accumulate a count related to the time during which pairs of similar samples are sensed by its exclusive-OR gate during each signalling interval. The integrator registering the highest count at the end of a given data interval signifies the data element received during that interval.