Specifications

18
Figure 17 Telephone wiring closet
6 Telephone – Connection to the World
We have three phone lines. Two lines are for family use and the third reserved for business. ADSL is
installed on the business line.
The two non-business lines are configured as a hunt group. If
line 1 is busy incoming calls are automatically sent to line 2.
Hunting is unidirectional; if someone calls the second line and it
is busy the phone company will not ring the first line.
Residential service reps may not be familiar with setting up a
Hunt group because it is a "business feature." You may have to
press the rep a little to get it. It is especially nice because it is
free; the Telco does not nickel and dime you with feature
charges. Line 2 is optioned with call waiting, so even if both
lines are busy the caller will not get a busy signal. The goal was
to treat the two personal use lines as single main phone number;
callers always use the main number. This works well for
incoming calls, however outgoing calls are not as simple.
We wanted both lines to return Caller ID of the main phone
number. Unfortunately that is not possible, caller ID is bound to
the specific line. The choices for the second line are to allow
Caller ID or disable it. Disabling Caller ID hides the phone
number from ordinary users, however some people block
incoming calls with Caller ID turned off. If Caller ID is left on
people will learn the second number and may call it directly,
defeating the purpose of the hunt group. We opted to enable
Caller ID and remind family and friends to use the main
number.
The third line is reserved for business use. It is not part of the
hunt group. Since the business has only a single line we wanted
to use Telco based answering service. Telco answering service is a good match for single line offices
because the caller gets voice mail if the line is busy instead of a busy signal. I consider call waiting
inappropriate for a business connection. Unfortunately our local central office does not support voice mail
so we must rely on an answering machine. Another possibility is to use call forwarding to automatically
transfer the call on busy or no answer to a cell phone.
We did not want to dedicate a line solely for dialup modem use, as this seemed overly restrictive. However
sharing one line for both modem and phone poses a mutual interference problem. Picking up a phone
dumps the modem. On the other hand computer has no way to know the phone is already in use, causing it
to attempt to dial even if the phone is in use. I looked for an off the shelf solution to this problem but could
not find one. So the Modem Access Adapter (MAA) was designed. This eliminated the need for a dedicated
modem line and provides optimum use of the phone lines.
Usage Tip – Call waiting can be disabled at the beginning of the call, disabling call waiting for the
duration of the call. The sequence varies by locale, in our area it is *70. Unfortunately if you send
the disable sequence to a line not equipped with call waiting it is interpreted as part of the dialed
number, resulting in an incorrect connection. This is a problem if the modem uses multiple lines
and not all are equipped with Call Waiting. The V.92 standard allows the modem to automatically
hold the connection when it detects call-waiting tones. This allows the new call to be answered
without dropping the Internet connection.