In television games programs may be stored on tape, disc or similar to change a basic games unit to different games or other entertainment or instruction. The data is transferred from the recording medium to a processor and clocked in at a suitable rate. The invention provides generation of clock pulses using two counters. The arrangement generates clock pulses at a predetermined position of data 1's but for 0's it generates clock pulses a predetermined interval after the preceding pulse. An arrangement is provided recording staggered data on two tracks of a tape to counter drop outs and a watermark code is provided to guard against use of unauthorized programs.