) [2 marks] What is half-duplex transmission and what flow control is needed for ) [1 mark] How many signal levels will be required to encode 4 bits in a single ) [3 marks] In general, how is it that faster speeds can be achieved over the same ) [4 marks] Describe controlled access and contention-based access to a physical half-duplex transmission? symbol? optical fibre as technology improves? medium? Which is centralized and which is distributed