Channel Groups

Channel Groups displays all the channels available and lets you group channels together by signaling type. You can also modify or delete existing groups. To create a channel group, click Create Channel Group. This displays the Channel Group Configuration page.

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WARNING: Switchvox restarts after you create a new channel. Any current calls are dropped, and any agents logged into queues are logged out.

Device Types

Device Type describes the type of line that is connected to the PBX through this device. The following options are available:

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E&M Signaling. The E&M (Ear & Mouth) Signaling device type is a different type of T1 signaling used by some telephone companies. E&M signalling describes certain older T1 lines. Select this option if you have an E&M or E&M-wink circuit, sometimes referred to as a Supertrunk.

Callback Extension

This is the extension to ring when a voice call comes in over this provider or channel. Callback extensions can be any extension type (your receptionist’s phone, an IVR, etc.).

Default Fax Extension

This is the extension to ring when a call comes in over this provider or channel, and is identified as a fax. (Switchvox only identifies T.38 faxes over SIP providers. A fax coming in over an IAX provider or a channel, or a fax using a different standard may not be identified as a fax.)

Advanced Options

It is unusual to change the Advanced Options, so they are hidden. If you find that you need to change an Advanced Option, click Show Advanced Options.

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Acoustic. This experimental echo canceller is tuned for acoustic echo. While good on paper, this method of cancellation hasn't worked very well in practice.

Fax Buffer Policy

Set the Fax Buffer Policy for this Channel Group. To turn this option off, select Disabled. The default is Half. This option lets you set a buffer policy to prevent fax failures on high latency systems. See the related option "Number of Fax Buffers." You must install a fax license and the fax software to make faxing available. For details, see the “Digium Addon Products” article.

Fax Detection

Set the Fax Detection for this Channel Group.

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NOTE: You must install a fax license and the fax software to make faxing available.  For details, see the “Digium Addon Products” article.

Fax Error Correction Mode

Error Correction Mode (ECM). The default is to leave this feature enabled.

Hang up on Polarity Switch

Some countries, most notably Australia, signal remote hangup by switching the polarity of the lines. This is sometimes called ROIC (Reverse On Idle Condition). Only enable this option if you have confirmed with your telco that hangups are signalled with polarity reversal.

Hardware Echo Cancellation

This option enables the hardware echo cancellation module on BRI cards.

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Minimum transfer rate for fax transmissions. Minimum transfer rate used during fax rate negotiation. The default minimum transfer rate is 2400.

Network Specific Facility Code

This option is rarely used. If you are unsure of what to do, leave it set to None.

NSF, or Network Specific Facility codes are special codes that are sent in PRI facility messages and are used to signal additional data to your telephone company. Do not change this setting unless your telephone company explicitly stated that they require a specific NSF value.

Number of Fax Buffers

Set the number of fax buffers. The default is 12. This option lets you set a buffer policy to prevent fax failures on high latency systems. See the related option “Fax Buffer Policy.” You must install a fax license and the fax software to make faxing available. For details, see the “Digium Addon Products” article..

Overlap dial

Overlap dialing sends each digit pressed as it's entered, instead of sending the entire number all at once. It is safe to leave this option disabled.

Pause Before Dialing

This option adds a slight delay to allow the off-hook signal to propagate to the telephone company before sending down DTMF digits. This should not need to be changed.

PRI Dialplan

This controls how outbound calls are sent over the PRI. Check with your PRI provider to confirm which method they prefer.

PRI Reset Interval

The default value for this option, 3600, is usually correct. This controls how often the PRI B channels are reset when they are unused. For the vast majority of PRI lines, this has no effect on the PRI and is purely done just to be safe. However, some PRIs in countries such as India may have problems with being reset. In that case, you may want to enter a value of never.

PRI Switch Type

Your PRI provider should be able to provide you with the preferred PRI Switchtype. The most common option is National ISDN 2, sometimes referred to as NI2.

Relax DTMF Recognition

Enabling this option will make the DTMF interpreter much more permissive. If you are having trouble receiving DTMF key presses in IVRs with calls over a channel group, enabling this option may help. Unfortunately, it also may result in many more false positives, or double keypresses. In cases where poor line quality is hampering DTMF detection, it is highly recommended to improve the line quality first before enabling this option.

Ring Debounce

This option is only used in very rare circumstances in certain countries. This option controls how long Switchvox waits before confirming a ring on analog lines. The value is in 1/8000ths of a second, and the default is 1024. Larger numbers cause Switchvox to wait longer, potentially making it harder to receive false-positives or ghost calls. Smaller numbers cause Switchvox to be more sensitive to rings.

RX Gain

We recommend enabling ***Automatic Gain Correction *** before altering this option. This controls the volume of audio received from this channel group. For example, if incoming callers are too quiet or too loud, this option can change the volume. Values are in decibels, and can be positive or negative to make calls louder or quieter respectively. This is usually only needed on analog lines (not T1 lines) to compensate for signal loss in the wires. Normal values range in the -15 to 15, and it's recommended to start low, and increment the gains by a factor of 2 until they reach the correct volume (e.g., 2, 4, 6, 8...).

Secondary Device Type

This option should almost always be set to PRI (Primary Rate ISDN) CPE Side. Consult your T1 provider before selecting an alternate option.

Train echo canceller at beginning of calls

This option sends a pulse at the beginning of a call in the attempt to pre-train the echo canceller. This can improve situations with echo at the beginning of a call.

TX Gain

This controls the volume of audio sent from this channel group. It is recommended to not increase this value, although lowering it to -3 may improve call quality and/or echo. If in doubt, leaving this setting at the default of 0.0 is recommended.

Use Caller ID

Enabling this option will enable receiving (and sending) caller-id. It is almost always recommended to leave this set to Yes. The one situation where it may be preferable to disable caller-id is when using analog lines in a country (such as the USA) that sends the caller-ID between the first and second ring. In order to receive caller-ID on analog lines, Switchvox has to wait until the second ring before answering. If caller-ID is disabled, Switchvox will answer inbound calls immediately, without waiting for the caller-ID.

Wait Duration

This forces the system to wait the specified number of seconds before answering the call, allowing time to receive all of the call data before answering the call. The default is 1. Most likely you do not need to change the default.