Which of the following is not a way that a company can implement VoIP?

a. Replace an existing PBX voice tie line.
b. Upgrade the company's existing PBX.
c. Switch the company over to a partial IP telephone system.
d. All the above are ways to implement VoIP.

c. Switch the company over to a partial IP telephone system.
Explanation: Three ways a company can implement voice over IP (VoIP) telephony into its network are to replace an existing PBX voice tie line (for example, a T1 circuit) with a VoIP gateway, upgrade the company's existing PBX to support IP telephony, or to switch the company over to a complete IP telephone system.