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Conference Call Tech Bulletin from

The person making the conference call on the phone system can hear the outside parties OK, but the two outside parties have a hard time hearing each other.

I hear this all the time! Actually, I've been hearing it for over 30 years. Even some old electro-mechanical phone systems would do conference calls - as badly as today's modern systems do on POTS lines.

This Bulletin also applies to phone systems that have a feature that transfers a caller outside of the business, using two lines, often called External Call Transfer. All those systems do is conference the two lines together, without having a caller in the middle staying on the line while they talk. Without an inside caller on the conference, the off-premise transfer is usually a little better than a regular conference call.


If you don't want to know why it's not working, here's the quick and easy solution to low volume on conference calls that I've been using for over 25 years on every new phone system I've installed:

1. Order 3-Way Calling from the phone company on all the analog CO lines

2. Program a Flash Key on every phone if it's not built-into the phones

3. Train the users to hit the Flash button when they're talking to someone (on an incoming or outgoing call), hear the boop boop boop boop, dial the number they want to conference in, and hot the Flash button again to conference everybody together.

Since the conference is being done in the CO on the 4-wire side, the volume of the conference will be perfect for all parties - inside and out.

If you are selling one of the phone systems with an amplified conference, you don't need to do this (well, maybe).

Technically speaking if you have T1s / PRIs or SIP trunks you shouldn't need this because they are "four wire" trunks with separate transmit and receive (see further explanation below) - so there won't be feedback if the gain is boosted.

BUT, some systems just have a crummy conference even using four wire trunks. 3-Way Calling (using the flash button to make a conference call on the same trunk) may not work on the T1 / PRI lines or SIP trunks, so there may be no fix for the problem. You'll have to try it on any particular installation.


Most phone companies offer the feature Off Premise Transfer on their POTS lines. It works just like the phone company's 3-Way Calling, except when you hang-up after making the conference the call is transferred to the other party, rather than you having to stay on the conference. You need to be able to do a hookflash on the CO line, just like you do with 3-Way Calling.

This is the same feature that Centrex uses to allow a Centrex user to transfer the call to another extension, or to an outside party. Some phone companies may not have bought that feature from their CO vendor, so it's probably not available on all exchanges in your area (the phone company will say, "It's not tariffed").

This method of External Call Transfer is much better than using the phone system to transfer the call outside, since the phone system will use two lines and this only uses one line until the transfer is made, and then it's using no lines. The volume between the two parties is perfect because the call is connected on the 4-wire side of the phone company's equipment, just like a normal phone call.

Most of the companies trying to do an Off Premise Transfer (External Call Transfer) want to do it automatically from their Automated Attendant. There's no reason an Automated Attendant can't do it if it can do a flash on a CO line, except the people who design most Automated Attendants and voice Mail systems are clueless and don't include that ability. It's not rocket science. They just don't know anything about phones.

We do sell the Ultimate Call Handler that you can put on a single line station port on a phone system. You would program it to answer the call transferred by a human or Automated Attendant to the station port, do a hookflash, dial the code to do a CO line hookflash, dial the number you want to transfer the caller to, and hang-up. If you can do all that with a butt-set on the analog station port, you can do it with the Ultimate Call Handler. (try it with your butt-set first!)

You can do the same thing with the Ultimate Call Handler if you can't get Off Premise Transfer using the phone company's 3-Way Calling feature (you need 3-Way Calling on all the POTS lines you'd ever want to transfer, just like you'd need Off Premise Transfer on all the POTS lines you'd want to transfer if your phone company offers it). In that case you would transfer the caller to the analog extension with the Ultimate Call Handler, do a hookflash, dial the code to do a CO flash, dial the number you want to transfer the caller to, do another hookflash, dial the CO line flash code again, and the incoming caller is connected with the person you wanted to transfer the caller to through 3-Way calling from the phone company. In this case, the Ultimate Call Handler will stay on the line until the call is finished. But only 1 line is ties up, and the volume between the parties is perfect because it's all being done on the 4-wire side at the CO.

When using these methods you have to take traffic into consideration. How many Ultimate Call Handlers and analog station ports (in a hunt group) will you need to handle as many calls as you need to simultaneously transfer? Or you need to program the Automated Attendant to take a message or do something else if the extension with the Ultimate Call Handler is busy.


For multi-party conferences, Conference Bridges with special hybrid circuits are available for 2 wire lines which separates transmit from receive, turning them into 4 wire lines for the purpose of adding the correct amount of amplification in each direction to make the conference call sound good, and then turning them back into 2 wire lines.

Modern Conference Bridges use DSPs (Digital Signal Processors) to separate transmit from receive and amplify the lines, which do a pretty good job (not cheap). Older Conference Bridges use analog circuitry and work OK except that there is less separation between transmit and receive. Since there's less separation, and the transmit side can see the receive side more, there is some chance that there will be feedback or ringing during the conference call from time to time.

You can buy a conference bridge that will work on analog station ports (or POTS lines). Well, it works sometimes. A conference bridge made for a T1 is likely to work correctly.

It's definitely overkill if you only want to add someone into the call you're on. For arranged multi-party conferences a conference bridge works well.

The biggest problem using a conference bridge is that the person setting up the conference needs to have a cheat sheet of how to add parties to the conference (it's usually not obvious). But they can get used to that pretty quickly. It would be the same when using one of the zillion dial-in conference bridges that charge per minute (which is a reasonable solution for more than two party conferences).

We don't have anything to do with this company, and I've never used their stuff, but I've never heard anything bad about Forum Communications conference bridges (I've recommended them to a lot of companies through the years):

A conference bridge works well on phone systems that send an open loop disconnect (CPC signal) out the analog station port when the outside party hang-up. Unfortunately, most phone systems don't provide an open loop disconnect on analog station ports. That means that without checking to make sure the conference bridge is compatible with any particular system you're installing it on, when one of several parties on the conference hangs-up you may get a busy signal, reorder tone or howler tone - making it impossible for the others to continue the conference.

Forum says that they don't have that problem as long as some audio is sent from the analog station port when a party hangs-up. They said that most systems send out in-band signaling, which can be a dial tone, reorder tone, howler or DTMF digit (usually an A or D tone). Their bridge is smart enough to split the line and listen for audio on each individual channel (not passing the audio to the other station ports in the conference, which would drop all the stations).

The problem comes in when the station port is silent when a party drops off, but the bridge may still drop off correctly a few moments later when the phone company sends their howler tone (after a message to hang-up the phone, which would interrupt the conference for a while).


This Bulletin applies to phone systems using phone lines that have 2 wires. Phone lines delivered digitally, like on a T1 / PRI or VoIP (without a two wire ATA), probably won't have the same problems with conference calls since those trunks are actually 4 wires, with separate transmit and receive pairs.

Because regular phone lines have 2 wires, both transmit and receive are on the same pair. That means that when you try to amplify the lines enough to make a conference call sound decent, you'll hear squeal, ringing or feedback.

Some older systems have analog 4 Wire E&M trunks, which can be conferenced without a problem since they also have separate transmit and receive pairs and won't cause feedback when amplified enough to make the conference call sound OK. Not many of those types of lines left out there.

Can the phone system manufacturers build "good" conferencing into their phone systems? Yes. Do most do it? No.

Considering that conference calls have been a feature on phone systems for over 30 years, and here we are making calls on our computers and through the Internet (and used-to fly to the moon), you'd think the manufacturers would feel bad about including a feature that obviously doesn't work (and hasn't worked for decades)?

I personally use the Flash Button type conference using 3-Way Calling from the phone company on our POTS lines every day. It always sounds great to all parties. It even works well on our SIP trunks (which we use for outgoing - we only use POTS lines for incoming calls).


For multi-party conferences most companies have turned to one of the zillion conference services that have sprung up. You can find tons of them on Google.

While they used to be expensive, competition has forced prices down. Since many use VoIP on their end, the quality is not the same between providers. Try them out to see when you get, but you generally get what you pay for.

There are two types of conference services:

1. You setup the conference yourself by calling the parties or telling them to call a number at a certain time.

2. Pay more and have an operator do the dirty work for you.

Setting up a conference by calling into a designated number at a designated time can be intimidating for both the users and the guy controlling the conference from his touch tone phone. Even so, it's probably the best solution to multi-party conferences.

Another option for many conference services (and built-into some VoIP phone systems) is recording the conference call automatically.