What's the meaning of technical manager?how to manage more than 20 worker/operator?manager have high technical point of view/high management skills?

both skills, obviously he must be technical, and managerial skills can be improved

You need to have extensive knowledge in your field and how to interact with your team professionally.

Technical manager need to know the internals of the function and not just the functional part of operation or system or work function. Internals says about what it makes to work (technical info) rather saying how it should be and how it works (functional info).

Typically It is impractical to manage big team directly under single head. A right effective management can be done with identified few leads -2 -4 among20 and delegate and track the activities closely with the identified resources. It would give the manager complete view & greater control.  

Manager can be techno-functional (technical) or functional, why I had said techno-functional is because all technical managers are techno-functional and one need to have understanding of the functional aspects without which the functional behaviour of the system cannot be acheived technically.

First of all being manage some thing or someone you should be managed, have enough knowledge and able to handle different people more tactfully and with respect, giving each member personnal attention and recognition and valur their comments.

My answer will be the manager should have

1- Experience as how to take decision and his outcome is quality or quantity, does he know how to let the employees to understand their work  

2- He knows the entire process

3- He knows the employees under him

4- to check the process from time to time

a good manager is always open minded and also tactical decision maker, so just manager do manage things tactfully thats become a good manager