DISTINCTIVE RING BASICS
Many telephone companies offer
Distinctive Ring (DR) services for your incoming telephone line.
With a standard telephone line, when an incoming call occurs, your phone
rings. The standard ring cycle is
six seconds long with a 2 second ring and 4 seconds of silence.
When you purchase DR service
from your telephone company, you get a second telephone number that uses the
same telephone line. When someone
calls the second number, the resulting ringing changes it’s sound.
The result is usually a ring-ring sound with 2 shorter rings, each about
1 second in duration. This is sometimes referred to as the first DR pattern.
Many telephone companies also
offer the option for a third telephone number and a third ring pattern.
This ring pattern is a ring-ring-ring sound with 3 rings, each less than
about one second in duration. This is sometimes referred to as the second DR
pattern.
NORMAL RING PROCESSING
When a modem is initialized for
use by software, a series of initialization strings are sent to the modem.
Each string tells the modem how to handle various telephone events.
A typical modem initialization will involve 5 to 10 separate commands on
operation. These commands are
installed as part of the modem driver when the modem is initially installed in
the PC.
Most modems can support
distinctive ring in two ways. The
first is at the ring level. If no
specific DR initialization is enabled during the modem init process, then the
modem will issue the data RING each time the telephone rings. As a result, each 6 second ring cycle will result in one RING
event coming from the modem.
When the first DR pattern is
involved for a DR call, most modems will just report two RING events for each
six second ring cycle. Then by
counting the time duration between RING events, software can determine if this
is a DR call.
If no modem DR initialization is
used, and the second DR pattern (ring-ring-ring) occurs, most modems will NOT
correctly report 3 RING events.
MODEM DR PROCESSING
When DR is enabled at the modem
level, the modem changes the data delivered with incoming calls occur.
Normally a modem sends RING events for each phone ring.
When DR is enabled, you usually get DRON and DROF events (ring on and
off) with the ring times. The time
values can then be used to determine which ring pattern is occurring.
Standard rings are 2 seconds on and 4 seconds off.
The first DR pattern is a ring-ring sound with ring times less than one
second each. The third DR is a ring-ring-ring, with even shorter ring times.
Modem level DR is enabled using
a DR modem initialization string. The
string for most current modem products is AT+VDR=1,10.
If the DR string is not already
in the initialization cycle for your model,
you can add it using a feature of the software: