Updated:  5/17/09

• Broadband
  If you have ADSL from your Phone Company, you probably need to keep a phone line. Some DSL providers will now put ADSL on a dedicated pair (you don't need a phone line), called Bare ADSL. If your broadband connection isn't reliable, your VoIP phone service won't be reliable.
  
  The more bandwidth you have in each direction the better for VoIP. If you can get SDSL (Synchronous DSL), where the speed is the same for both downloading and uploading, that would be good (harder to get, and usually more expensive). A real data T1 would be 1,500K both up and down, which is as good as you can get - but if you fill up that pipe with music or video downloads etc., your calls will still sound bad.
  
  Consider getting a separate broadband (DSL or T1) connection just for voice if you're planning to use only VoIP lines. It will save a lot of grief later. Having two totally separate CAT5 networks in your office, one for VoIP and one for data, makes the most sense.
  
  
• Bandwidth
  Bandwidth is the most important component of any VoIP telephone service. We've all heard calls that are garbled or choppy, and it's always because of a bandwidth issue (either on the local network or somewhere on the Internet).
  
  With most VoIP providers, you need about 128K for each VoIP telephone line, in both directions. If you have four lines, you need 512K both upload and download. Most ADSL lines are very fast downloading, maybe 1,500K, but they limit the upload speed to maybe 384K. That means that even if you aren't uploading stuff from a PC to the Internet while you're talking, you don't have enough bandwidth to have four people talking at the same time - you'd need at least 512K upload speed. In this case, you'd probably hear the other people OK (with your 1,500K download speed), but they'd have a hard time understanding you (it would sound garbled).
  
  On some broadband connections, like Cable, your connection speed will be reduced when a lot of other people in the neighborhood are using their Cable Modems, so your voice calls will sound worse during that time. If you use a computer on the Internet at the same time, things will really get garbled from time to time. If you have a 1,500K T1, and the company selling you the T1 only has two T1s feeding the neighborhood with 20 customers (3,000K), if other users are downloading stuff totaling 2,500K that only leaves 500K of bandwidth for your VoIP calls - even if you're paying for a whole T1. Probably OK at a home, but it doesn't give a good impression at a business.
  
  You would have the same issues using a Hosted PBX, where you use electronic VoIP telephones with buttons and a display connected to your office Ethernet network. These phones "talk" to a PBX located somewhere else in the city (or world... but closer is always better).
  
  A Hosted PBX will give you more features that are easier to use than with a standard single line analog phone, without your having to buy a phone system at all. Problems arise from the fact that all of the signaling and voice packets have to travel through your office, through your ISP (Internet Service Provider), and through the Internet to the Hosted PBX service provider. If you had a direct T1 to your Hosted PBX provider that doesn't use the Internet, the service should be perfect (if the Hosted PBX doesn't go down, and the Hosted PBX service doesn't get their phone lines over the Internet).
  
  
• Number Portability
  It's OK to port a real phone number to the VoIP company (it usually goes through eventually), but you won't be able to take the VoIP phone company's number to another phone company (don't give out any numbers the VoIP provider gives you - ever). Most VoIP providers "rent" the numbers from another company, so the numbers aren't theirs to give you.
  
  If a company other than a real phone company or LEC (Local Exchange Carrier) tells you that you can keep their phone number forever, don't believe it. Because most CLECs (Competitive Local Exchange Carriers) and VoIP companies "rent" their numbers from other companies, if the company who actually owns the number decides to exit the business for one reason or another, and the number can't be ported for one reason or another, the number is lost forever - not yours forever. Always get your phone number from a real phone company (LEC or ILEC - Incumbent Local Exchange Carrier), like Verizon, Quest, AT&T, etc. Then port it to the CLEC or VoIP company of choice once it's in and working (the LEC could still take it away from you, but that's very rare).
  
  It's also possible that an 800 number could also be taken from you, but again that's rare. Because the 800 number service provider owns the 800 number, not you, it's possible for someone to hijack the 800 number and for you to lose it (by mistake or on purpose).
  
  
• Battery Backup
  None of this stuff works without power, unlike a real phone line. None of it takes a lot of power, so a good sized battery backup from the computer store will probably keep it going for quite a while (if the batteries are good, but most batteries go bad within a couple of years - and you find out during a power failure).
  
  
• Alarm System
  It probably won't work on a VoIP line without some changes. Although some VoIP providers tell you to simply plug their VoIP device into the nearest jack - after disconnecting the Phone Company's line where it comes into the building, the alarm won't work that way. Coordinate VoIP with your alarm company.
  
  The reason the alarm won't work is that the alarm is using tones to communicate, like a modem or sometimes like a touchtone phone. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress modem tones or other tones, they often just don't make it to the other end so that equipment can understand them.
  
  Your alarm company may be able to hook up your alarm system so it transmits on the Internet instead of a phone line, but that doesn't make much sense since there's a good chance the Internet won't work when the alarm goes off (Murphy's Law).
  
  Keep a real phone line for your burglar or fire alarm!
  
  
• Ground Start Trunks
  Some PBXs are setup to use Ground Start Trunks. A Ground Start Trunk is dead for outgoing calls until the phone system puts ground on the phone line (the ring side) for maybe a quarter second. Ground Start trunks are thought to help reduce "glare," where someone is trying to make an outbound call and actually gets a new incoming call because the trunks are all pretty busy.
  
  Most VoIP boxes and cable company boxes only offer Loop Start Trunks, where all it takes to get dial tone is to go off-hook. Even if the VoIP box or cable box can be optioned to provide a Ground Start Trunk, the provider probably doesn't know what a Ground Start Trunk is.
  
  Some older phone system required a different trunk card for a Ground Start or Loop Start Trunk. Some have jumpers or programming options for Ground Start/Loop Start. In any case, if your system requires a Ground Start Trunk and you give it a Loop Start Trunk, you won't be able to call out, incoming calls may or may not ring, all the lines may be busied out so no lines work at all, and you may get phantom ringing (incoming calls with nobody there).
  
  
• E911
  If people are used to dialing 911 to get the police, and it doesn't work, it could be bad. Most VoIP providers give you stickers to put on the phone that say "911 might not work." Write the local non-emergency number on the sticker.
  
  
• Telephone Book Listings
  You may or may not be listed in the white or yellow pages, or 411.
  
  I don't know if this works, but there's a free service that will help you get listed in real phone books: www.listyourself.net
  
  
• Caller ID Displayed
  The name and/or number that people see on their Caller ID box when you call them may not be yours, and it may even say Cellular Call, Out-of-Area or Unavailable when you call someone (depending on who the VoIP provider rents their numbers from).
  
  
• VoIP Voice Mail
  Some VoIP providers force your calls to go to their Voice Mail if they aren't answered in X rings. Ifyou don't want to use their voice mail, that can be a problem.
  
  
• Network Down Option
  Most VoIP providers will automatically forward calls to the number of your choice if their main system can't communicate with your VoIP device. This is critical:  Put your cell or some other number in that field!
  
  Read the SLA (Service Level Agreement) carefully for any service you decide to use for incoming calls. Keep in mind that 99% uptime means your phone number won't work for over 7 hours out of the month.  A 99.99% uptime means that your phone number won't work for over 4 minutes a month.
  
  The uptime numbers probably won't include  intended downtime  for maintenance of the servers or routers at the VoIP provider's data center, normally done in the middle of the night. That could add an hour or more of downtime a month (which you essentially never see on a phone line / voice T1 from the real phone company).
  
  If you're just using VoIP for outbound, getting cut-off once in a while or not being able to make outbound calls once in a while isn't a big deal (especially when you consider the savings over real phone lines). Not being able to receive incoming calls could cost you a lot more than the savings.
  
  Here is an example SLA from a business VoIP provider:
  

  XXX will credit its customers with a half of the month's charges for down-time caused by failure of it's server/switch that exceeds three hours in any month. VoIP has some inherent risks with interruptions of bandwidth and Customer Premise Equipment (CPE), like routers and ATAs, so naturally this is not covered. You should have confidence in our server/switch, and we back it up.
  

• Fax
  Works OK with some VoIP providers (you may need a "special" line/device).
  
  The reason faxes won't work is that the fax is using tones to communicate, like a modem. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress fax tones, they often just don't make it to the other end so that equipment can understand them.
  
  
• Modems
  Might work at slower speeds? Probably not.
  
  The reason modems won't work is that the modem is using tones to communicate. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress modem tones, they often just don't make it to the other end so that equipment can understand them.
  
  
• Credit Card Machines
  They don't use fast modems, but they still may not work on VoIP lines.
  
  
• TV Set-Top Boxes
  Some cable or satellite set-top boxes have an option in programming to make it work with VoIP. Probably won't work without your changing something.
  
  
• Water, Gas or Electric Meters
  Some utilities have spent big bucks to install modems on their meters so they can read them remotely. There's some chance that the modem won't work with a VoIP line. When your utilities are shut off, you'll know for sure.
  
  
• Echo
  Sometimes you just can't get rid of it. It depends what's causing it (see our Echo Tech Bulletin below).
  
  
• Incoming DTMF Digit Recognition
  Sometimes Automated Attendants or Voice Mail Systems don't recognize DTMF digits when people call in, usually intermittently.
  
  
• Automated Attendant or Voice Mail Disconnect
  Some VoIP devices don't send a disconnect signal (like the real Phone Company usually sends). That means that when the outside party hangs-up after leaving a message, there may be a lot of silence or busy signals at the end of the Voice Mail message.
  
  Likewise, if someone calls in and hangs-up before making a selection on the Automated Attendant, the now disconnected call will end up ringing the phone programmed to get calls if someone just "waits" and doesn't dial an extension number (doesn't make the real person doing this happy).
  
  Many companies solve that problem by disabling 0 (the operator) entirely. Screw the stinkin' customer.
  
  
• Ringing
  Some VoIP devices will only ring a single phone. The phone company provides 5 REN worth of ringing. Most VoIP devices provide less. Many provide under 75VAC, which is the minumum a phone company is supposed to supply (VoIP companies aren't really phone companies - even though they claim to be, so they don't have to adhere to any standards).  A Ring Voltage Booster is available.
  
  
• Garbled Voice
  Test it before you commit. Test it at different times of the day, and with different loads on your own network. Even if it sounds good to you, call many people and ask them how you sound. The VoIP providers think if the other party sounds good to you, you'll think their service is great. In reality, you may sound garbled to the other party, and it may be at a low volume. Where you put the VoIP device on your network may make a difference.
  
  A phone that connects with a USB or sound card connection (screen phone) will be very dependent on what you're doing on that particular PC. It would be best to do nothing while you're on a call.
  
  When you test the VoIP quality, be sure to have someone call you from that line when you're on a regular phone line. Most VoIP service providers have learned that if they make the call sound OK to the person using the line locally, their service won't be cancelled for quality issues as quickly. In many cases, they tilt the bandwidth so that the call sounds fine to the local caller, while it's garbled or choppy to the person on the other end. Try it many times, at different times of the day, before deciding whether to keep the service (most offer a 30 day moneyback deal of one kind or another).
  
  
• Hiss
  There's a hiss, or background white noise on some VoIP lines. Sometimes it's there all the time, sometimes just on some calls. Listening to the background noise on these calls is very tiring if you have to be on the phone all day.
  
  
• Drop-outs / Cut-offs
  Test it before you commit. Test it at different times of the day. It's often worse at different times of the day, depending on your type of Internet connection (T1, DSL, cable, etc.) and the general traffic at your ISP / on the Internet. If there are a lot of people watching/downloading movies in your neighborhood at the same time, VoIP could become very garbled.
  
  If you're planning to use VoIP between two locations (like an office and branch office or home worker), consider using a VPN (Virtual Private Network). A VPN will encrypt the SIP (VoIP) packets that carry the conversation (and any other data you send like email and spreadsheets, etc.). That encrypted connection is called a VPN tunnel.
  
  VPN routers are inexpensive and easy to setup these days. You'll need one for each end of the connection.
  
  The reason to encrypt your VoIP traffic is to prevent your ISP from blocking/degrading the quality of VoIP calls by messing with the SIP packets, which are easy to identify as they go through their routers. Why would they do that? Because they probably are or own a phone company in addition to offering broadband. If your VoIP sounds terrible, you're more likely to switch to their phone service (which is almost always a better quality than VoIP, even if they call it VoIP themselves).
  
  
• Delay After Dialing
  Some VoIP providers have a long delay after the last digit dialed before your call goes through. That can sometimes be fixed by adjusting the number of digits they're expecting. Sometimes their service is just screwed up at different times of the day (or during a full moon?). Sometimes a particular VoIP phone might require that you hit * or #  after your number, to start dialing.
  
  
• Support
  Before committing, call or email VoIP customer service a few times to see if you can live with that level of support.
  
  
• What happens if you don't like the VoIP service after a while?
  It's better to think about this now, rather than when it happens. Paying an extra fee to drop the service before the contract is up isn't that bad. Making sure now that you can get phone service from another vendor is important.
  
  
• What happens if the VoIP company goes out of business?
  It's better to think about this now, rather than when it happens. You can hear a couple of stories in our Things to Think About Before Ordering VoIP.
  
  
  

The reality of the economy is that if you're reading this, you've already decided to switch to VoIP to some extent to save money. You may not consider my suggestions of things to check out first, but at least when something doesn't work to your expectations you'll have an idea of why... because you've already read about it.

Check out Things to Think About Before Ordering VoIP for a much more detailed list of CLEC, Cable and VoIP phone line quirks.

If you're having echo problems, take a look at our Echo & DTMF Problem Tech Bulletin.