Internet Customer Solutions, Inc

SIP Lines versus Direct Inbound Dial (DID) Telephone Numbers

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A SIP Line or a SIP Calling Path is the connection from your IP PBX or Cloud PBX to the SIP Provider, which connects to the PSTN (Public Switching Telephone Network) or the old phone switching company such as Verizon, AT&T, etc. A SIP line can handle maximum one active call. If a call is put on hold, and another call is taken, only one call is active. This means that one SIP line can handle this situation. 

If your company needs to handle on the average six simultaneous calls, then you need six SIP lines. 

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At least one DID or a Telephone Number is needed to identify your business.  If certain employees want to have their own telephone number, a DID needs to be given to each one of them.

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With an IP PBX or a Cloud PBX, each employee will get an active extension number.  If certain employees want to have also their own telephone number, they will need also a DID besides their extension number. You can use a passive extension number for just forwarding calls to a cell phone of an employee who is never in the office. 

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An example of a certain phone set up:

• Needs

  • Your company has 10 employees who are most of the time in the office. SInce not all of them call at the same time, you guess that maximum 6 employees call at the same time. Only four employees need besides their extension, their own direct phone number or DID since they are sales people or executives who need to be called directly, and whose phone number needs to be seen by the caller for call backs. 

• Solution​

  • A PBX with 10 extensions is needed. ​

  • A SIP trunk is needed with 6 SIP lines, and 5 DIDs (one for the business, and four for four employees). The metered plan of NUSO for this case will cost $72 + (5 *$1/DID) = $77/mth.