pronunciation help. What does the simple /i/ means

The cambridge dictionary phonetics use phonetic symbol /i/ in addition to /I/ and /i:/

I assume they use the DJ phonetic transcription. The other source I read says that /i/ is the old spelling for /I/, but that apparently can not be the case because Cambridge dictionary lists /i/ separately alongside /i:/ and /I/ in their help page. Can someone explain to me what does it entails, is it just a shorter version of /i:/?

Thanks in advance.