Caller ID and Distinctive RingPage 1
Caller ID and Distinctive Ring
Ordinarily, when a call comes in on an ordinary telephone line, the phone rings. Distinctive ring is where the cadence of the ring can be changed by the exchange. For example, the normal Australian “ring-ring” might be changed to three short rings “ring ... ring ... ring”. Distinctive ring can be used to indicate calls to two or more different telephone numbers associated with the one physical telephone line.
Caller ID is where the exchange sends information down the telephone line in the silent period between the first and second ring cadences. Suitably made telephonic equipment, such as some modems, can decode this information to give a display of the telephone number of the telephone which was used to originate the call.
Adaptive answering is where an incoming call is answered and some telephonic device works out whether the call is a voice call, a fax call or a data call. Then the call is treated appropriately. So a voice caller will hear an outgoing message, then might leave their own incoming voice message. A fax caller will be able to send a fax. A data caller will be able to establish a data connection.
Caller ID happens first, then distinctive ring, then the answer happens (that is, the modem goes off hook), then adaptive answering occurs.
Caller ID
Caller ID information is sent on the form of a string of characters, using a standard modem modulation, Bell 202. The carrier speed is 1200 bit/s. The data throughput is 120 char/s. About 3 seconds is available. A variety of information can be sent, but the most common is the telephone number of the calling telephone line. The Maestro Woomera modem supports Caller ID and can display the Caller ID on its front panel display.
Caller ID must be enabled at the answering end. A telephone company will normally charge a fee to have Caller ID turned on. Caller ID must also not be blocked by the caller. Most callers do not block their Caller ID going out, but some, such as public telephones, always do.
Distinctive Ring
Telstra’s Faxstream Duet is an example of a distinctive ring service. A second telephone number is allocated to an existing telephone line. The original telephone number is retained. Which number has been called can be indicated by different "distinctive ring" cadences, easily distinguished by ear -- and by suitably made telephonic devices. Distinctive ring can be used to distinguish between different incoming call types, such as voice or fax. There are two rings commonly used, DR0 and DR7. DR0 is the traditional Australian ring-ring sound, with two rings. DR7 is the ring cadence Telstra wants to use for fax, it consists of three short rings. Telstra's distinctive rings are different from the US equivalents. All Maestro modems support distinctive ring.
For example, to make the modem respond only to the DR7 ring cadence (three short rings), include "-SDR=4" in an initialisation string sent to the modem. The modem will ignore all ring cadences except those with three rings. It will report incoming three-ring cadences as "RING3".
Distinctive ring is often used to indicate the call type, thus discriminating between a fax or voice call at the time of the incoming ring. That is convenient for people with an ordinary telephone on the same line as the modem (or a fax machine). However, the distinctive ring actually tells you nothing about the call type, it actually tells you which number the caller has dialled. It would be quite possible to receive voice calls on the fax number or faxes on the voice number.
Adaptive Answering
Adaptive answering is where the modem (in conjunction with the software) works out what type of incoming call (voice, fax or data) it is, after the modem has answered. All modern fax devices produce fax calling tone (CNG) immediately after dialling. Data calls can be set (using the ^ dial modifier) to produce V.25 calling tone, which has a different frequency and cadence from fax CNG tone. Voice calls produce no calling tone. All Maestro voice modems support adaptive answering. After the modem answers, it starts off assuming that the call is a voice call and begins the outgoing voice message. Meanwhile, it is listening for fax or data calling tone. If it hears fax calling tone then it switches to receive the fax. If it hears data calling tone, a data connection is negotiated and a host mode program is started, which looks like a BBS to the incoming caller. The caller can then upload/download files, etc. Naturally, all this stuff can be selectively turned on and off in the software. The host mode can have passwords to give a greater or lesser degree of privilege to various incoming callers. Instead of a BBS program, data callers could be given remote access to a LAN, or an Internet connection, or whatever other data service you feel like setting up.
Having Everything
Distinctive ring could be used with adaptive answer to do things like having the voice number for people who want to speak to you, but if they want to leave a message then they call on the fax number. It would be possible to have one telephone line with several different distinctive ring numbers, each one of which could do adaptive answering. Each number could have a different outgoing message and a different data service.
It would be possible to set up the software so that calls from certain Caller IDs would be treated differently.
All this would need just one modem. Alas, there is presently no software known to me which supports all that.