Transmission means the physical shares will still be transferred to the transferree in terms of for the following example:
It is applicable to those where the physical shareholder has expired and the nominee failed to transfer the shares in his or her name or for married ladies who are willing to change their name after marraige.
Only in such case transmission in terms of physical shares will be allowed on or after 5th December 2018.
Transposition means for example
Partial change is name
If a person's name as per AADHAAR and PAN is Amit Kumar Singh
Whereas on physical shares it's Amit Singh,
then such change from Amit Singh to Amit Kumar Singh on share certificate will still be done for physical shares on or after 5th December 2018..
That's why whatever shares you have as on today in physical form, get it dematerilised as soon as possible.
Else there is going to be lot of trouble later on.