Additional hints for emulating "real" telephone service (Sipura adapters only, may also apply to Linksys adapters that use Sipura technology)

In this section we will just mention some Sipura adapter defaults that you or your service provider may want to change in order to provide service that better emulates regular wireline telephone service. Except perhaps for the first, these are NOT essential settings, and none of them in any way affect call quality. To change these settings, go to the web interface for your Sipura adapter (enter the local IP address for the Sipura in web browser), then click on "advanced" in the upper right corner of the screen, then click on the "Regional" tab. If this tab is not visible you may need to do an "Admin Login", which requires a password, or you may need to ask your VoIP provider to make the desired changes for you. Please note that the tone settings shown below are for the United States and Canada only.

•In case you missed it above, in the U.S. and Canada, under Ring and Call Waiting Tone Spec, the Ring Voltage should be set to 90 and (this is most important) the Ring Frequency to 20 — this not only allows older phones with mechanical bells to work, but it just might help in a few odd cases where Caller ID doesn't seem to work properly on a particular phone. In fact, if you have any weird problems with equipment that worked fine with traditional phone service not working with VoIP, and that equipment is activated by a ring signal, this may be the problem. Sipura adapters default to a ring frequency of 25 Hz, which is NOT the frequency usually used in the United States and Canada.
•Also as mentioned earlier, under the Control Timer Values (sec) section, we suggest setting CPC Delay to 10 and CPC duration to 1, because if you have one or more phones with a "hold" button and you ever put a call on hold and then no one picks it up, this will release the hold (freeing the phone line) when the caller hangs up. Note this will not help if you accidentally leave an outgoing call on hold — at present the Sipura doesn't have any good way to release outgoing calls accidentially left on hold automatically (perhaps Sipura might consider adding this in a future firmware release — it would great if they would add an "Off Hook Warning Disconnect" signal, which would be like a CPC disconnect, except that it would activate just before the Off Hook Warning Tone plays).
•Lengthen the dial tone to 20 seconds (some people find the default 10 seconds too short): Change Call Progress Tones | Dial Tone to 350@-19,440@-19;20(*/0/1+2)
•Lengthen Second Dial Tone, Outside Dial Tone, Prompt Tone, Busy Tone, Reorder Tone, MWI Dial Tone, and Cfwd Dial Tone to 20 seconds: These settings, like the basic dial tone mentioned above, are under Call Progress Tones - in all the existing strings find ;10( and change it to ;20(
•Left a phone off hook accidentally? Found that the Sipura's off hook warning tone borders on pathetic? Here's a much better one. This gives you 30 seconds of warning warble tone followed by 30 seconds of the genuine off hook warning tone used by most phone companies: Change Call Progress Tones | Off Hook Warning Tone to 480@-10,620@-16,1400@0,2060@0,2450@0,2600@0;30(.2/0/1,.2/0/2);30(.1/.1/3+4+5+6)
Note that if for some reason you don't want the warning warble (which we highly recommend because it will cause most people to hang up before being blasted with the off-hook warning), you can use 1400@0,2060@0,2450@0,2600@0;30(.1/.1/1+2+3+4)
Obviously, you should not make either of these changes if you made the change to generate the "D" touch tone prior to the Off Hook Warning Tone, as described under "Special considerations for business customers" above. [The pertinent section is copied below]
•If you have an answering machine or similar device that accepts touch tones for control functions, and you find that when you call in and try to use tones to activate the unit it does not respond properly, check under the Miscellaneous section to see what the DTMF Playback Level and the DTMF Playback Length are set to. The default DTMF Playback Level is -10.0 which is often too low, while the default DTMF Playback Length is .1 which is very often too short.
•A few people may wish to go into the individual "Line" tabs ("Line 1" and "Line 2") and go to the FXS Port Polarity Configuration section, and set Caller Conn Polarity to Reverse. All this will do for most people is give you an audible "click" when a call you place is connected, and again when the called party hangs up. What it actually happening is that the polatity of the line is reversed when the outgoing call is connected. Some advanced phone systems may be able to use this information to avoid the "line left on hold" problem, but most "hold" buttons on telephones will NOT release just because line polarity reverses (you may be able to build a circuit that responds to polarity reversals and generates a CPC disconnect signal after a polarity reversal). Note that if for some reason you want the line polarity to reverse when you are the called party, then you will need to set the Callee Conn Polarity to Reverse.
•Finally, if you have changed any of the above settings (as opposed to your service provider), you will want to make sure that you go to the "Provisioning" tab and set Provision Enable to no. However, most commercial service providers will not allow you to do this, since it prevents them from making changes to your service (which could overwrite the changes you have made above). That is why, if you want any of the above settings changed and you are a commercial VoIP service customer, it is better to get your service provider to make the changes in their system so that any future updates will not overwrite the changes.

By the way, one way to avoid a line left on hold is to not use a hold button on a telephone, but instead use "flash hold" — hit the flash button (or flash the hookswitch), then when you hear the second dial tone, hang up. Your phones will emit a short ring every few seconds until you pick the line back up, so unless you have the ringers turned off, it will be pretty hard to forget about the call on hold. This gives you a way to put a call on hold on one phone, and then pick it up at another. Some VoIP providers may disable this capability, though we don't know of any that do, and also we do not know if this works with any brand of VoIP adapter other than Sipura.

..... certain VoIP adapters do not generate what is known as the CPC signal. Without getting into a long technical dissertation, this is a momentary drop in power on the line (as if the line were completely disconnected for a few moments), or a polarity reversal on the line. Either of these signals can be used to cause telephone hold circuits to release automatically. The CPC signal (but not the polarity reversal) can also be useful with some consumer grade equipment, including telephones with "hold" buttons and some types of answering machines. However, most residential customers won't notice much of an impact from the lack of the CPC signal.

On a "normal" telephone line, this voltage drop or polarity reversal usually occurs if you hold the line open after the other party has hung up (to a person listening on the line, it sounds like either just a single click, or a click, a VERY short pause of "dead air", and another click. But in either case, it happens very quickly so if you're not paying close attention you could easily miss it!).

As mentioned, the purpose of this signal is to release a line inadvertently left on "hold." So, when connecting a small business phone system that is designed to work with regular business phone lines to a VoIP adapter that does not supply the CPC signal, the problem appears to be that if a call is accidentally left on hold, the line will never release. In some slightly more expensive systems, it's possible to "park" a call while waiting for another extension to pick it up, and a "parked" call might never be released without manual intervention. Thus, probably with distressing regularity, the line gets held open because someone put a call on hold and forgot about it, and with no CPC signal the line was never released.

If you think you have this problem, contact your VoIP provider — they may be able to enable CPC on your adapter. For example, Sipura adapters have CPC settings under the "Regional" tab — try setting "CPC Delay" to 10 and "CPC Duration" to 1 — your VoIP provider may have locked out these settings; if so, they would have to change these settings for you. But note that Sipura's CPC functions only on incoming calls; it will do nothing to help a situation where an outgoing call has been abandoned on hold. If you really need a CPC-like disconnect following outgoing calls using a Sipura adapter, there is one thing you could try, if you have access to the Sipura's advanced settings. Go to the "Regional" tab, under Call Progress Tones, and set the Off Hook Warning Tone to 941@-16,1633@-16,1400@0,2060@0,2450@0,2600@0;1(*/0/1+2);30(.1/.1/3+4+5+6)
This will generate one second of a "D" touch tone (941 Hz + 1633 Hz) just prior to playing the Off Hook Warning Tone. The "D" tone cannot be generated from a standard 12-button touch tone pad, but can be used directly by some types of equipment as a disconnect signal. If your equipment cannot be directly programmed to release a line upon hearing the "D" tone, you can buy a "DTMF Flash Generator" that should disconnect the line upon hearing the "D" tone (see next paragraph).

Assuming that none of the above suggestions work, we can point you to a place where you can probably find a solution to this problem, but please be aware that we've not personally tested any of this equipment. Reports from actual users of this equipment would be welcome. Go to Mike Sandman's "Wizard's Tool Box" page and scroll about ¼ of the way down the page — search for the items entitled "CPC GENERATOR", "MAKE A SILENCE DETECTOR, TO CREATE A CPC SIGNAL", and "CallSaver: Disconnects a Phone Line that's Left Off Hook!" ONE of these devices will probably solve your problem, depending on the VoIP adapter in use and how it actually reacts when a phone is left off-hook after the call is ended (for example, VoicePulse returns a fast busy signal when the other end disconnects, and Vonage sometimes does this as well, so from the descriptions given it is likely that the "CPC GENERATOR", which detects a dial tone or a busy signal, would be the device to use to create the CPC signal). If you have a Sipura adapter and can reprogram it to generate the "D" touch tone as described in the above paragraph, then the "DTMF Flash Generator" (not quite halfway down Mike's page) may be able to listen for it and generate a useable CPC signal.