home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Software Vault: The Gold Collection
/
Software Vault - The Gold Collection (American Databankers) (1993).ISO
/
cdr11
/
sp144man.zip
/
SIX.TXT
< prev
next >
Wrap
Text File
|
1993-04-19
|
23KB
|
610 lines
SPORTSTER 14,400
CHAPTER 6. DIALING AND ANSWERING
BEFORE CONNECTING
For two modems to connect and exchange
data, they must use the same modulation
standard and, for error control to be
successful, the same error-control
protocol.
Modulation/Standards
The Sportster 14,400 modem conforms to
the following modulation and signaling
standards.
CCITT V.32 bis 14.4K/12K/9600/7200/4800
bps
CCITT V.32 9600/4800 bps
CCITT V.22 bis 2400 bps
Bell 212A/
CCITT V.22 1200 bps
CCITT V.23 1200 bps with 75-bps
back channel (sometimes used
in U.K. and Europe)
CCITT V.25 Answer sequence for
calls originating outside the
U.S. and Canada
Bell 103/
CCITT V.21 300 bps
CCITT V.42 LAPM error control, 1200
bps and above
CCITT V.42 bis Data compression, 1200
bps and above
MNP Levels 2, 3 and 4 error
control, level 5 data
compression, 1200 bps and
above
CCITT V.54 Analog, digital and
remote digital loopback
testing
Setting the Transmission Rate
Setting your software to 38.4K or 19.2K
bps ensures that the Sportster 14,400
can operate at its highest rate. The
modem detects the rate from the AT
command, operates at that rate at the
serial port, and tries to connect with
remote modems at 14.4K bps, its highest
connection rate.
Follow the guidelines in Chapter 3,
Quick Start, or the more detailed
instructions in Chapter 4 before
selecting either variable or fixed
serial port rates (&Bn). If your
software supports a fixed serial port
rate, set the modem to &B1 and your soft
ware to a high serial port rate for the
best throughput. Set the modem for flow
control (&Hn), as well.
We recommend leaving the modem at its
link operation factory setting, &N0,
unless your application requires that
you specify a fixed connection rate.
&N0 allows the Sportster 14,400 to auto
matically negotiate with the remote
modem for the highest possible
connection rate.
Data Format
Both your machine and the remote
computer must use the same 10-bit data
format, which always consists of 1 Start
bit, plus one of the 9-bit combinations
listed in Table 6.1. You may have to
phone the remote computer installation
or BBS to find out what word length,
parity and Stop bit combination is
required.
Before calling, set your communications
software (or terminal if you are using
one) to the required scheme. Some commu
nications programs use a kind of
shorthand for formats, such as 7-E-1 or
8-N-1. The modem detects the format
from the AT prefix of the next command
it receives from your keyboard or from
your software.
Table 6.1_Allowable Data Formats
Word Parity Stop
Length (1 Bit) Bits
7 Even, Odd, 1
Mark, Space
7 None 2
8 None 1
Error Control
For reliable high-speed data transfer,
always set the Sportster for error
control, &M4 (default) or &M5, for calls
at speeds over 2400 bps. Most users
communicating with V.42- or MNP-
compatible modems will want error
control at 2400 and 1200 bps, as well.
The &M command is described in Chapter
4.
If you're dialing out, it's a good idea
to find out if the remote modem is MNP-
compatible. Some public network
services, for example, are not. If the
remote modem doesn't have MNP capa
bility, it may misinterpret the MNP
error-control request and block a
successful connection. If you know the
remote modem doesn't support MNP, dis
able MNP handshaking by setting Register
S27 to 16 (ATS27=16). The modem still
connects with V.42-compatible modems and
modems that do not perform error
control.
To reset the modem for normal opera
tions, issue the ATZ (reset) command,
or set Register S27 to zero.
PLACING CALLS
This section discusses commands used in
the following operations.
Dialing D (0-9 # * , / ; " ! P T
W @ R), DS
Redialing A/
Canceling dialing<any key>
Dial (D)
The following command example instructs
the modem to stop the display of
commands (E0, turn off the local echo),
turn off the speaker (M0), and dial (D)
the phone number (1234567) using Touch-
Tone dialing (T). The spaces shown are
ignored by the modem and are only
included here for readability.
AT E0 M0 DT 1234567 <Enter>
When the Dial command is issued, the
modem goes off hook_ the equivalent of
picking up your phone_then enters
Originate mode and dials the number
sequence that follows. The modem also
executes any other commands or options
included in the command line.
The dial string may include up to 40
characters. The modem counts but
ignores punctuation characters such as
parentheses and hyphens. It does not
count spaces, the AT prefix or the
carriage return (Enter key) required to
execute the command.
Cancel Dialing
To cancel Dial-command execution, press
<any key>. If you inadvertently hit a
key on the keyboard while the modem is
dialing, the call is canceled. If this
occurs, type the A/ command (explained
under Redialing later in this chapter).
On receipt of A/, the modem redials.
Dial Command Options
You may want to review the many options
on the next several pages that are
available for tailoring Dial strings.
The most typically used are the Dial
Type, Pulse or Tone, and the Pause
options_comma, slash and W.
Dialing Type, Pulse or Tone
The modem is shipped to default to pulse
(rotary) dialing. To have the modem use
tone dialing, which includes the
asterisk (*) and pound sign (#), use the
T command.
Dialing type commands may be included in
the Dial string (ATDT number), issued
separately (ATT or ATP), or included in
the &W default configuration string you
write to NVRAM, as explained in Chapter
5. You can also set the X2, X3 or X4
result code options, which include
adaptive dialing, explained next.
NOTE: You can switch from one dial type
to another within a dialing sequence.
Keep in mind that the modem remains set
to the last dialing type instruction
until it is reset (ATZ command) or it
receives a different dial-type command.
Adaptive Dialing (X2OX4)
When any of the X2 through X4 options is
in effect and you do not issue a dialing
type in the Dial string, the Sportster
14,400 uses tone dialing, which is
faster than the default pulse type. How
ever, if the phone company's central
office does not have Touch-Tone
detection equipment, the modem cannot
break dial and continues to detect the
dial tone. If this occurs, the modem
automatically reverts to pulse dialing.
Pause (,)
A comma causes a two-second delay in the
dial sequence. The following example
contains four-second delays at several
points.
ATDP 9,,7654321,,55555,,1 312
1234567 <Enter>
The first four-second pause is to access
an outside line after dialing 9, but you
may wish to use the W option, described
below. The second pause is to make sure
the remote system is ready for the
user's account number, and the third, to
delay before dialing the long-distance
number.
Such pauses, however, may not be
necessary. Experiment and use delays
only as required.
Slash (/)
A slash (/) can be used in any command
string to make the modem pause for only
125 milliseconds. Some users find it
helpful to have the shorter delay of a
series of slashes, rather than the 2-
second comma pause.
Wait for Another Dial Tone (W)
This command is useful in situations
where you must wait for a second dial
tone before continuing dialing. For
example, if you need to dial for an
outside line, as in the following exam
ple, the Sportster 14,400 continues
dialing as soon as it detects the next
dial tone.
ATD9W1234567 <Enter>
NOTE: This command executes only if
result code option X3 or greater has
been issued. If the modem is set to X2
or lower, the modem interprets the W as
a comma (two-second pause).
Dial and Return to Command Mode (;)
If your phone is plugged into the modem,
you can use this option to have the
modem Auto Dial a telephone rather than
a modem. The Sportster 14,400 dials,
remains off hook and returns the OK
message, indicating it is in Command
mode.
For example, to have the modem place a
voice call, enter the Dial command with
a semicolon.
ATDT5551234; <Enter>
When the modem returns the OK result,
pick up your phone receiver so you can
talk to the other party, and send the
command that hangs up the modem.
ATH <Enter>
Similarly, you can call a recorded
weather or other service. Have the
modem Dial, listen to the recording over
the modem's speaker and, when you are
finished, instruct the modem to hang up.
Dialing Letters (I)
Quotation marks are used to make the
modem dial abbreviations and acronyms
used as phone numbers, such as DIAL USR
(the USRobotics Sales Department's 800
number). The option is called Quote
mode. Quotation marks are inserted at
the beginning of the alphabetic string.
ATDTIBBS NEWS <Enter>
NOTE: If you are including another
command after the dial string, use
closing quotation marks before the
additional command.
Transferring Calls (!)
This command applies to modems in
installations where other modems share
the phone line. The modem flashes the
switch-hook, that is, it goes off hook
0.5 seconds, on hook for 0.5 seconds,
and off hook again to dial the specified
extension. The following example
includes instructions to return to Com
mand mode (;) and to hang up (H).
ATDT !1234;H <Enter>
Wait for an Answer (@)
Some online services answer the phone
and return a tape-recorded request for
information before processing trans
actions. In such instances, the @
command can be used in the Dial string
to tell the modem to detect at least one
ring, wait for five seconds of silence
at the other end of the call, and then
continue to execute the Dial string.
To use the @ command, set the modem to
X3 or X4. If the modem is set to X2 or
lower, the modem returns an ERROR mes
sage when encountering the @ character
in a command string.
In the next example, the modem is set to
the X4 result code option and dials a
banking service. Each occurrence of @
in the example indicates a five-second
wait for silence, that is, for taped
requests from the bank for a password
(12345), an account number (6789) and a
transaction code (2). The transaction
code might indicate, for example, a
request for an account balance.
ATX4 DT5551234 @ 12345 @ 6789 @ 2
<Enter>
If the necessary conditions do not
occur_no rings, or no following five
seconds of silence_the modem times out
as it normally would (after 60 seconds).
It then sends the message NO ANSWER to
the screen and aborts the command.
Reversing Originate/Answer Frequencies (R)
This command allows calls to an
originate-only modem. It reverses the
modem's originate/answer frequencies,
forcing the Sportster 14,400 to dial out
at the answer frequency. The command
follows the Dial command, before or
after the phone number.
AT D1234567R <Enter>
AT DR1234567 <Enter>
Dialing the Stored Number (DS)
Chapter 5 includes instructions for
storing a frequently-used telephone num
ber in nonvolatile random access memory
(NVRAM). To have the modem dial a
stored number, use the DS command.
ATDS <Enter>
Redialing (A/)
The most frequent reason for redialing
is receipt of a busy signal. Use the A/
command, which does not take the AT
prefix or a Carriage Return, to redial.
A/
When the modem receives a command, it
stores it in its command buffer until
it receives the next AT command. Note
that if you've sent the modem an
additional command since the Dial
command, A/ repeats that command
instead of redialing.
ESCAPE CODE OPERATIONS (+++)
Once the modem is online to another
system, the only command it recognizes
is an escape code of three pluses, which
forces the modem into online-command
mode. Issue the command in the
following sequence.
∙ Wait one second after sending the
last item of data
∙ Type: +++
∙ Wait one second before typing any
data
Do not type the AT prefix or a Carriage
Return. The guard time of one second
before and after the code prevents the
modem from misinterpreting the presence
of +++ in the transmitted data stream.
If necessary, the character used in the
escape code or the duration of the guard
time can be changed by resetting
Register S2 or S12. See the S-Register
Summary in Appendix B.
Modem Response to +++
When the modem receives +++, by default
it enters online-command mode and
returns the OK result code. It
maintains the connection and is ready
to act on commands. You may then
choose one of the following options.
∙ Issue commands to the modem and
then return it online. This
operation is explained below under
Returning Online.
∙ Hang up the modem, explained in the
next section.
Alternatively, if you want the modem
automatically to hang up on receiving
the +++ escape code, set S-Register S14
to 1 (ATS14=1). The modem disconnects
and sends the NO CARRIER result code to
the screen.
Hanging Up (Hn)
At its default setting, the escape code
forces the modem into online-command
mode but leaves the line open. To hang
up the modem, issue the following
command, with or without the zero, once
the modem sends the OK result code.
ATH <Enter> [or ATH0 <Enter>]
H0 Hang up (go on hook).
H1 Go off hook.
If you want to issue commands to the
modem and have it return online, use
the next option.
Returning Online (On)
After forcing the modem into online-
command mode with the escape code
sequence, you can issue commands and
then toggle the modem back online with
the O command, as in the following
example.
AT Q1 O <Enter> [or AT Q1 O0
<Enter>]
O0 Return online (normal).
O1 Return online and retrain. If
errors occur during a non-ARQ
connection, try this option. The
modem returns online and requests
that both modems resynchronize.
O2 Return online and shift rates. If
errors occur during a non-ARQ, 2400-
bps connection, and the remote
modem also supports this O2
feature, use it to force the modem
to shift down to 1200 bps for more
reliable data transfer. As line
improvements occur, the modems can
be forced to shift up again to 2400
bps: send the +++ code and, after
receiving the OK code, send ATO2.
This feature is part of the CCITT
V.22 bis recommendation, but is not
commonly implemented. Make sure
that the remote modem has the
capability of shifting between 2400
and 1200 bps before using this
option.
AUTOMATIC ANSWERING
The Sportster 14,400 is shipped with DIP
switch 5 DOWN, Auto Answer suppressed.
To set the modem to automatically answer
incoming calls, do one of the following.
1.Before powering on the modem, set DIP
switch 5 UP. When you turn the modem
on, the modem answers incoming calls
on the first ring.
2.When the modem is on, use software
control. The following command
instructs the modem to answer on the
first ring. (You can substitute a
higher value. See the S-Register Sum
mary in Appendix B.)
ATS0=1 <Enter>
When the modem senses a call coming in,
it sends the result code RING to your
screen, goes off hook, and sends the
remote modem a high-pitched answer
tone. If there is no Carrier Detect
within 60 seconds, the modem hangs up.
If the connection is made, the modem
returns a CONNECT result code. When
the
call is disconnected by you or the
remote user, the modem hangs up and
returns the NO CARRIER code.
Suppressing Auto Answer
To disable Auto Answer, reverse Steps 1
or 2 above: set DIP switch 5 DOWN
before powering on the modem, or set the
modem to answer on zero rings.
ATS0=0 <Enter>
Manual Answer
If you've disabled Auto Answer but are
expecting an incoming data call, use the
Manual Answer command. Send the modem
the following command after the RING
result code appears on your screen.
ATA <Enter>
When the call is disconnected, the modem
returns to its original state, Auto
Answer disabled.
Points to Remember
1.You can set the modem to receive
calls when you're not at your
computer or terminal. Load your
communications software as you
normally do, and set the modem to
Auto Answer. Also set your soft
ware's file-save function to save
incoming messages and/or files.
2.If you've attached your phone so it
can be used for conventional calls,
disable Auto Answer when you are not
expecting incoming data calls.
Otherwise, your modem may answer the
phone before you do, greeting a voice
caller with a high-pitched,
irritating answer tone.
INTERNATIONAL CALLS
The following commands apply to
international calls.
CCITT/Bell Answer Sequence (Bn)
To answer international calls, use the
default B0 setting.
B0 This setting is required for V.32
bis modems to answer V.32 bis
calls. It also selects the CCITT
V.25 answer sequence, used outside
of North America.
The B0 setting does not affect the
modem's ability to call or answer
domestic modems. It takes slightly
longer, however, to connect.
B1 This setting selects the Bell 2225
Hz answer tone used in the U.S. and
Canada, but will prevent your modem
from answering domestic or
international V.32 bis calls.
Guard Tone (&Gn)
British phone switching systems require
answering modems to send an 1800 Hz
guard tone after they send an answer
tone. Some other European phone
networks require a 550 Hz guard tone.
Guard tones are not used in the United
States or Canada.
&G0No guard tone, U.S./Canada.
Default.
&G1550 Hz guard tone follows answer
tone. Requires B0 setting.
&G21800 Hz guard tone follows answer
tone, United Kingdom and some
Commonwealth countries. Requires
B0 setting.
Pulse Dial Make/Break Ratio (&Pn)
This command sets the ratio of the off-
hook/on-hook (make/ break) interval for
pulse dialing. The default sets the
modem for use in North America. The
ratio must be changed if the modem
is used to dial out in the United
Kingdom and some Commonwealth countries.
&P0Make/break ratio, U.S./Canada:
39%/61%. Default.
&P1Make/break ratio, United Kingdom,
some Commonwealth countries:
33%/67%.
CCITT V.21_300 bps
Select this option to call or answer
overseas modems at 300 bps. In V.21
mode, the modem answers Bell 103/V.21
calls, but only originates V.21 calls.
This option is enabled in Register S27
with the following command.
ATS27=1
CCITT V.23_1200/75 bps
Some United Kingdom applications require
a 1200-bps speed with a 75-bps back
channel. This option is enabled in
Register S34 with the following command.
ATS34=8