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Calling Number Display (CND) Fax Routing

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Calling Number Display (CND) Fax Routing

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RelayFax is equipped with support for routing incoming faxes based upon Calling Number Display (commonly called Caller ID) data. As with other methods of routing inbound faxes, this is accomplished by using the Inbound Fax Rule editor. You will create rules specifying the text for which RelayFax will search and then the actions that will be taken when that text is or isn't found.

There are a few requirements that must be met before you will be able to route faxes based upon Calling Number Display (CND) information. First, the CND service must be active on the telephone line on which you receive faxes. This service is provided by your telephone company, usually for a small extra monthly charge. Also, your receiving fax modem must have support for detecting and preserving CND data so that RelayFax can acquire it, and that support must be enabled. Since CND support is not normally enabled by default for most modems, it is likely that you will need to add the appropriate command to your modem's INIT string within RelayFax. Consult your modem's user manual for the proper INIT string command that enables CND support. See Modem Properties for information about editing your INIT string.

Many inexpensive modems do not have CND capability.

CND data is transmitted from the telephone company to your fax modem in a packet of information between the first and second ring. Therefore, you must configure your modem to allow at least two rings before answering the call if you want to be able to route messages based on CND data. You can configure this setting on the Modem Properties dialog.

CND data can be provided to RelayFax in a variety of formats. It can be sent as a raw byte stream, in single-message format, or multi-message format. To make full use of RelayFax's CND routing capabilities you must configure your modem to provide CND data in multi-message format. Consult your modem manual for the proper INIT string settings required to achieve this (for example +VCID=1). In multi-message format most modems append "labels" to the raw CND data elements in order to make it easier to read, but there are no uniform standards governing what these labels should be. Therefore different modems use different labels for each piece of CND information. One modem, for example, might label the CND number as "NUMB=" while another would use "CALLER NUMBER:". Because RelayFax needs to know which labels your modem uses so that it can parse the number and name elements from the CND data, you will need to determine them and then enter them into the controls found on the Modem Properties dialog. You can determine them by watching for the labels in the main display during an incoming call being processed by RelayFax. Technically, RelayFax should be able to acquire the CND data in raw format (which doesn't require any labels), but experimentation has discovered that some modems modify even the raw data before passing it to RelayFax. This makes parsing at the application level inevitable.

In addition to the normal actions that can be assigned to Inbound Rules, there is one special action available for use exclusively with CND routing. Since CND detection takes place prior to answering the call, you can use the "Do no answer incoming call" action. When an incoming call is ignored as a result of such a rule the call is not answered and will ring until the remote side gives up. While the phone is ringing you may see one or more error messages such as "unspecified modem error" or "timeout during fax send/recv". These error messages are of no real concern. The presence of these error messages does not effect the performance of the software in any way.

See the "DAT File Processing Macros" section for information regarding CND related macros available for use within DAT files.