Google has finalised a deal to buy phone management firm Grand Central Communications. 

Grand Central runs a web-based service that allows users to link and manage multiple phones through a single number and voicemail account. The service is currently in beta.

Terms of the deal were not disclosed, but media reports suggest that Google paid as much as $50m.

Grand Central will continue to operate its service as a beta, but will only be accepting new users by invitation. Google plans to keep the service active for the time being, but declined to reveal any long-term plans.

"I am sure that Google has a short and longer-term vision for the product," wrote Greg Sterling, founder and principal analyst for Sterling Market Intelligence, in a company blog. 

"And I am sure that there are some hypothetical advertising/calling dimensions to the longer term vision."

In the short term, the analyst suggested that Google is just trying to expand its reach.

"My guess is that Google saw a telephony platform like this as strategic in the sense that it creates more convenience, value and loyalty among users. It helps reinforce Google's brand and usage generally," wrote Sterling.

The analyst added that Google's long-term strategy may possibly include integrating the service into Gmail and Google Talk. 

Sterling suggested that Google may also include Grand Central's technology in a larger telephony offering similar to Skype's.