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phoneguyjr (Vendor) (OP)
9 Feb 07 16:33
We have a customer that would like to know the difference between IP phones(Avaya IP office, NEC Aspire, and the like) and Digital phones(Avaya Difinity, NEC DSX, and the like here). We need to know the best way to describe the difference, the benifits of each, and the disadvantages. Thanks. Matt
biglebowski (TechnicalUser)
9 Feb 07 16:48
VoiP has come on leaps and bounds in the last couple of years and in my opinion is now a very good solution. You also need to consider if they are planning to upgrade or replace, if budget is an issue and what they want to use them for (ACD, DID etc)

Advantages of VoiP

requires less management i.e phones can be moved easily, requires less cabling and IT staff don't view it as voodoo funny stuff.

Disadvantages.

If you lose your network backbone you lose your phones (although not such a big issue in a small office)environment

When I was born I was so suprised I didn't talk for 18 months

SYQUEST (TechnicalUser)
10 Feb 07 18:12
The thing is they are both "digital", but the coding methods and transmission format are different. Some are better than others...

....JIM....
Sympology (MIS)
12 Feb 07 6:52
Advantage of IP? Can locate phone 3000 miles away from system !
Disadvantge? Requires a solid, stable network.

Only the truly stupid believe they know everything.
Stu.. 2004

Helpful Member!(4)  JediBMC (MIS)
12 Feb 07 17:29
I can only speak from the Avaya side of the house, as that is where my experience is.  That being said, here is my best attempt at a description and comparison of VoIP and Digital.

Let us start with the definitions:
Digital Telephones
Descendants of analog telephones, digital telephones convert the analog voice signal into a digital signal and transport the signal across dedicated copper lines to a central switch.  The digital signal utilizes a unique communications protocol, such as DCP to control the transmitting of the digitized voice signal as well as programming codes that reference additional features.

Digital telephones are limited (much like analog telephones), in that they must have a direct connection to the central switch.  The direct connection can be through “home runs” or cross connect fields, but must be dedicated to the specific telephone.

VoIP Telephones
An emerging (ok, it has been emerging for a long time now) technology in telephony is VoIP.  This technology abandons the direct connection constraint of digital and analog telephone systems by leveraging the data network infrastructure.  By changing the telephone into a network device, administrators can place telephones where ever the data network is available, without need for a direct connection to the central switch, so long as the centralized switch also has a connection to the data network.  In the most simplistic sense, voice communications are converted by the telephone into digital signals which are then encapsulated for an Ethernet network and transmitted along side other Ethernet traffic.

While VoIP overcomes the limitations of digital telephones in the form of a direct connection, the new constraint is the quality of the data network.

Comparison
Reliability
Looking at it from the K.I.S.S. (keep it simple silly) standpoint, digital is a winner.  The communications between digital telephones and the central switch rely on the standard copper wire that has been around for decades in one form or another.  Trouble shooting is usually as simple as ensuring connectivity between endpoints and physical operation of the device.  Although VoIP has come a long way, it is still vulnerable to many of the hazards associated with data networks, such as broadcast storms, high latency, and re-transmits.  As more and more devices are added to a data network, the probability of the above mentioned hazards is enhanced.

Flexibility
Where there is a data port, there is a phone port.  That simplicity makes VoIP the winner in the flexibility category.  With additional expansion into Wi-Fi, there are few places that a VoIP phone can not be placed.  Unfortunately, digital telephones really don’t even show up for this category.

Expandability
This is probably the most difficult category to judge.  On the side of VoIP, you have an almost limitless number of stations… so long as the data network can support it.  For Digital, you can expand only as far as the physical facilities will allow.  In the end, it comes down to the specific environment.  Some facilities may have a decent data network and ample physical room.  For them Digital is easier to expand.  Some facilities have a highly tuned and scalable data network.  For those facilities, the answer is VoIP.  Overall, I think Expandability ends in a tie.

So, there you have it, my definitions and my assessment of Digital vs. VoIP.

I hope that helps!

-Brian-
Semper Paratus

phoneguyjr (Vendor) (OP)
13 Feb 07 17:39
Thanks, that last post was really helpful. We have been trying to convince this customer to stick to the switch in place or upgrading to a difinity or something in that range. There really are not that many extensions so a difinity almost seems overkill. The building uses wireless for the data network. the only Cat5E cables are the ones leading to the wireless access points. To us it didnt make any sense ripping up the walls to install Cat5E just so they can have VOIP phones. Thank you all for your posts and keep up with the good work on answering questions.
aarenot (Vendor)
25 Feb 07 23:50
wireless voip

Sympology (MIS)
27 Feb 07 7:42
[Quote}
wireless voip
[/Quote]

I really wouldn't try this. There are very few Wireless links good enough to cary voice at business class level. Ok for ocaasional users.
It's not the links that are the issue, but how they are used.

Stu..

Only the truly stupid believe they know everything.
Stu.. 2004

mextera (TechnicalUser)
2 Mar 07 18:02
JediBMC, has many great points and I agree with most!

Now from the NEC side.

Hybrid Technology takes both Digital, VOIP and marries the two technologies. Using TDM (digital) and VOIP in the same architecture allows for greater flexibility and reliability. A hybrid system uses Packet Assemble Disassemble to convert from TDM to VOIP and vice versa.

A true Hybrid Switch will allow user’s to assimilate to VOIP in a much slower and easier transition. While allowing critical Digital users the safety of the Digital World, new more flexible user’s can switch to VOIP.

My vote Hybrid! Not all useres are the same.

Mextera

Nazule (IS/IT--Management)
9 Mar 07 13:41
From the Nortel side I can say the Hybrid PBX to VoiP conversion is the only way to go if you are a large business.  If the customer is large having an invested intereset in existing digital systems using TDM it can be difficult to simply rip it all out and convert to pure IP overnight.  
I have two large campus environments over 400Km appart and we converted to IP in stages and are still doing so since 2004.  We started by converting our site to site trunking to IP, that ran for two years until our first roll out for user stations to IP.  In 2006 we rolled out a new facility completely on IP using our existing Nortel PBX.  All new facilities are planned as IP and as our network infrastructure is upgraded to POE (power over ethernet) we are upgrading those facilities to IP telephony.
This methodology allows for a slow rollout and coverage of areas of our campus that either do not require a full featured set (keep it analogue) or that may be cost prohibitive to upgrade the network backbone.

So break it down for the customer:
Cost of either solution based on the size of the company.
Is there a big network upgrade required? i.e. the PoE switches, additional bandwidth between sites currently using TIE trunks or other method.
Are there area's that you need the legacy TDM phones etc.
IP softphones also make life easier by installing software on the PC and not having another device on the desktop but this is not something for every user.

IP is the way to go for sure, it is just picking how you get there that is the question.  If their existing system cannot be a hybrid but the facility may warrent some TDM look at the system that does both easily and cost effectively.

Most pure IP switches have backwards compatable cards etc to handle TDM.

Gregson (TechnicalUser)
16 Mar 07 10:12
Digital is still the most robust system for internal use. It is tried and true, has better sound and the features are are more varied. A digital system can work outside of the network with its own PRI (T1) or copper service. For many this is good meaning that if the network goes down, the phones will not.

IP solutions. Everybody jumps on the IPs because it is the latest and greatest. They of course are on your computer netwoek with their own IP address. The benefits are: 1.when you have multiple site you can communicate through the network and call extension to extension. Also there is no added cost, like a regular phone call.2. If someone needs to traveland have network connectivity at another office or hotel, etc., with an IP phone they can call ext. to ext. as if in the office just like hooking up their laptop. A call from Japan would have no added cost.

Most systems allow both digital and IP and I would suggest this combo. Digital for in house and IP for remote calling.

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