Thanks to Laurent Delsarte for some of the research and writing for this
section.
A modem (MOdulator-DEModulator) is a device that modulates an analog carrier
signal to encode digital information for transmittal, and also demodulates
such a carrier signal to decode received transmitted information. The common
example from the main time period of the 8-bit Atari computers is the voice
band modem, otherwise known as a "dial-up modem" that turns the digital data
of a personal computer into modulated electrical signals in the voice
frequency range of a telephone channel. These signals can be transmitted over
telephone lines and demodulated by another modem at the receiver side to
recover the digital data. Thus, in this pre-Internet form of computer
networking, any two computers may communicate with each other over a standard
telephone line.
The first commercially successful modem was the Bell 103 from AT&T. While the
AT&T Bell System maintained monopolistic control over the direct connection to
its phone lines in the USA, third-party manufacturers could only offer
"acoustic" modem configurations. Acoustic modems featured a cradle designed
to fit snugly around the microphone and earpiece of a standard (of the time)
Bell telephone handset. A standard Bell telephone was utilized for it's
microphone, speaker, and dialing capabilities. Such modems were designed to
be interoperable with the Bell 103, which maintained its role as the effective
industry standard.
Later "direct-connect" modems, led by the Hayes Smartmodem, instead connected
directly to the phone line. These modems contained their own microphones,
speakers, and dialing capabilities controlled via software. The "Hayes
command set" successfully established the industry standard for controlling
modem features via computer software.
Most voice band modems have a pass-through line allowing a standard telephone
to be physically connected to the line while the modem is also connected.
However, voice and data cannot be transmitted at the same time over the same
phone line (as is possible with newer telecommunication technologies such as
ISDN and DSL). When online using a dial-up modem, before telephone services
like voice mail were common, incoming callers would experience a "busy signal"
as if someone was already talking on the line. This limitation was finally
addressed in 2001 with the V.92 modem standard. V.92 includes a "Modem On
Hold" capability, especially useful in combination with the phone company's
"call waiting" and "caller ID on call waiting" features.
A wide variety of modulation and communication techniques can be successfully
implemented over a standard telephone line. In order for two modems to
communicate, they have to initially successfully negotiate the technical
nature of the communications to be used between them. Connection
characteristics include modulation technique ("frequency shift keying", "phase
shift keying", etc.), operation mode (one-way "half duplex" or bi-directional
"full duplex"), synchronization ("asynchronous" data without clock signal or
"synchronous" data accompanied by separate clock signal), and bitrate
(measured in bits per second). Early modem users had to become familiar with
arcane settings such as these in order to establish successful modem to modem
communications. In time, modem modulation standards were established and
adopted by the industry, allowing for the details to largely become
transparent to the user. Newer modems would simply negotiate the fastest and
most reliable connection possible between them, given the best capabilities of
both modems. Major modem modulation standards:
Standard (Year appeared) Top Bitrate Baud(symbols per second)
Bell 103 modem (1962) 300 bit/s 300 (V.21 precursor)
Bell 212A modem (1977) 1200 bit/s 600 (V.22 precursor)
V.22bis (1982) 2400 bit/s 600
V.32 (1986) 9600 bit/s 2400
V.32bis (1991) 14400 bit/s 2400
AT&T V.32ter (1993) 19200 bit/s 3200 ("terbo"; V.34 precursor)
Rockwell V.FC (1993) 28800 bit/s 3200 ("Fast Class"; V.34 precursor)
V.34 (1994) 28800 bit/s 3200
V.34 (1996) 33600 bit/s 3429 ("V.34 Plus" or "V.34bis")
US Robotics X2 (1997) 56000 bit/s 8000 (V.90 precursor)
Rockwell K56flex(1997) 56000 bit/s 8000 (V.90 precursor)
V.90 (1998) 56000 bit/s 8000
V.92 (2001) 56000 bit/s 8000
At the time, it was very common for modem speed bit rates to be incorrectly
referred to as "baud" rates. Other than the early 300 bit/s / 300 baud
modulation standard this was never correct usage of the term. Baud always
meant "symbols per second" rather than "bits per second."
Two additional important modem standards emerged in 1990: V.42 error control
and V.42bis data compression. V.42 and V.42bis were implemented in some later
V.22bis and V.32 modems, and probably in all modems supporting V.32bis and up.
V.92 modems, which appeared in 2001, support V.44 data compression, an
improvement over V.42bis compression.
In the early 1980s popular early commercial online services reached via dial-
up modem included CompuServe Information Service, Dow Jones Information
Service, and The Source. In addition to CompuServe, later online services
popular with Atari users included Delphi and GEnie. Modem users would also
dial in to mainframe computer systems at universities, or they would log in to
privately-operated Bulletin Board Systems running on other personal computers.
As long-distance telephone services were billed by the minute, telephone bill
expenses were an important consideration.
Atari produced several modems for use with the 8-bit Atari computers. Each
Atari brand modem supports U.S. modulation communication standards only; Atari
did not market their modems in Europe.
Atari 830 Acoustic Modem
- Sold separately or as part of the Communicator kit CX484
- Type: Acoustic, frequency shift keying (FSK)
- Speed: Up to 300 baud
- Compatibility: Bell 103/113 modem compatible (U.S. industry standard)
- Additional hardware requirement: Atari 850 Interface Module or equivalent
- Connectivity: RS-232-C serial. Pinout:
14 25
o o o o o o o o o o o o DB-25 Socket - female
o o o o o o o o o o o o o
1 13
2. XMT Transmit Data (Input to modem)
3. RCV Receive Data (Output from modem)
5. CTS Clear to Send (Output from modem)
6. DSR Data Set Ready (Output from modem)
7. n/a Signal Ground (Common)
8. CRX Carrier Detect (Output from modem)
- Made in USA for Atari by Novation
- Based on the Novation CAT modem
- Top: Ready and Power LED indicator lights
- Side (left-to-right):
- "O / OFF / A" switch: Originate mode / Power Off / Answer mode
- Power input jack
- "F / TST / H" switch: Full duplex mode / Test mode / Half duplex mode
- Serial port
- Transmitter frequencies
- Originate: mark, 1270Hz; space 1070Hz
- Answer: mark, 2225Hz; space 2025Hz
- Receive frequencies
- Originate: mark, 2225Hz; space 2025Hz
- Answer: mark, 1270Hz; space 1070Hz
- Receive sensitivity: -45dBm
- Power: Uses an external power supply that delivers 20V AC @ 400mA, such as
the Atari #CA016751-01 / Novation 901017 or equivalent.
NOTE: Atari product catalogs variously list the minimum power rating for
the 830 at 7 watts or 18 watts)
NOTE: Both the 830 box and the 850 Interface Technical Manual indicate
that the 830 requires:
Input: 117V AC (4 watts)
Output: 24V AC @ 150mA
Is there an Atari-branded supply like this?????
- Shipped with an Atari CX87 Modem Cable (830 to 850 serial)
- Manuals:
- Atari 850 Interface Module Operator's Manual C015953 Rev. 1 1980
(preliminary version shipped with earlier/most 850 units; 102 pages)
- See Appendix 13: Atari 830 Modem, pages 97-102
- Atari 850 Interface Module Operator's Manual C017651 REV. B 1982 (15 p.)
- Contains instructions for both the 850 interface and the 830 modem
Atari 835 Direct-Connect Modem
- Sold only as part of the Communicator II kit CX488
- Type: Direct-connect modem
- Speed: up to 300 baud
- Compatibility: Bell 103/113 modem compatible (U.S. industry standard)
- Connectivity: 2 Atari SIO ports for direct connection to Atari computers
- MPU: Intel 8048 microcontroller (MCU), C060549
- Texas Instruments TMS99532 frequency-shift keying (FSK) modem chip, FC100279
- Made in USA for Atari by Racal-Vadic
- No speaker, but telephone sound can be routed to the computer audio output
- Pulse dialing only
- Power: external power supply that delivers 20V AC @ 330mA, such as the
Atari #C060479 or equivalent
NOTE: Atari product catalogs list the minimum power rating for the 835 at
18 watts, but Atari's own power supply is only rated for 9 watts)
- Manuals:
- The Communicator II User's Guide C024438
- Atari 835 Direct Connect Modem Field Service Manual FD100268
Atari 1030 Direct-Connect Modem
- Speed: up to 300 baud
- Compatibility: Bell 103/113 modem compatible (U.S. industry standard)
- Connectivity: 2 Atari SIO ports for direct connection to Atari computers.
- Uses SIO Motor Control; only one such device can be attached to the
system at a time.
- Made in USA; modem electronics by Penril
- Communications are possible with both originate-only and answer-only modems
- Built-in ModemLink telecommunications software
- Bootstrap without disk drive-- With no powered disk drive #1 present,
ModemLink (with integrated T: modem device handler) loads from the ROM of
a powered 1030 into computer RAM on system startup. (The 1030
masquerades as disk drive #1, responding to the Atari OS attempt to boot
from disk.) An extended beep is emitted through the computer's audio
signal as the program is loaded, then ModemLink runs.
- The T: handler can also be loaded from 1030 ROM into computer RAM later;
many alternatives to the 1030 ROM T: handler exist as well. Please see a
separate section of this FAQ list regarding R: and T: modem device
handlers for the 1030 for more details.
- Controls, software selectable:
- Full and Half duplex operation
- Pulse or Tone dialing
- Tones for tone dialing are generated by the computer and reach the
1030 via the SIO sound INPUT line (thanks to audio noise/leakage)
- Tone dialing not available on the 400 (Owner's Guide page 7)
- Memory buffer on/off
- Printer on/off
- Box sticker: "Free Time Offer Enclosed: Dow Jones News/Retrieval Service"
Shipped with CompuServe IntroPak as well
- Receive sensitivity: -43dBm
- Indicators:
- Power ON/OFF
- On-line (carrier detect) LEDs
- Included: Owner's guide, Atari SIO cable, Telephone extension cable with
RJ-11 clip connectors, Power adapter
- Power: external power supply that delivers 9V AC @ 5.4mA, such as Atari
#C062195 or equivalent
- User's documentation: C061798 (CO61798) The Atari 1030 modem with ModemLink
telecommunications program owner's guide (1983)
- Field service manual: ?????
- 1030 Designers: John Curran, Ken Fowkes, Sherwin Gooch (project director),
Joe Miller, Songly Mu, Bernie Poggi, Mark Rustad, Phil Schug, Dennis Smith,
Jose Valdes, Vince Wu
- Tone Dialer: * Original version by: J. W. Tittsler, Feb. 1983
* Final version by: M. D. Rustad, May, 1983
* Modified by: J. B. Miller, August, 1983
Atari XM301 Modem
- Type: Direct-connect modem
- Speed: up to 300 baud
- Compatibility: Bell 103/113 modem compatible (U.S. industry standard)
- Incompatibilities: Cannot be used with an Atari 1200XL (see Power, below).
The manual reads "You cannot use the XM301 modem with an Atari 1200XL
computer unless it has been modified. Contact your local Atari service
center for information on modifying your 1200XL computer."
- Additional hardware requirement: (none)
- Connectivity: Permanent SIO cable, must be at end of SIO chain
- Key engineer/designer: Jose Valdes at Atari
- Made in Taiwan
- No speaker, but telephone sound can be routed to the computer audio output
- Auto-dial and auto-answer capabilities
- Dialing capabilities: Tone and pulse (rotary) dialing
- Shipped with XE Term Communications Program disk (DX5076)
- Developed by Russ Wetmore for Atari
- Box sticker: "Free Inside/Special Offer: Money Saving Values from the
Source, CompuServe, Dow Jones News/Retrieval Service, Knowledge-Index, and
the Official Airline Guide."
- Transmitter frequency
- Originate: Mark 1270Hz +/- 0.5%; Space 1070Hz +/- 0.5%
- Answer: Mark 2225Hz +/- 0.5%; Space 2025Hz +/- 0.5%
- Transmit level: -9.0dBm to -16dBm
- Receiver frequency
- Originate: Mark 2225Hz +/- 30Hz; Space 2025Hz +/- 30Hz
- Answer: Mark 1270Hz +/- 20Hz; Space 1070Hz +/- 20Hz
- Sensitivity: -13dBm to -46dBm
- Carrier detect threshold
- On: -44dBm
- Off: -45dBm
- Bit error rate: No more than 1 in 10E5 bits
- Power: 5V @ 60mA, drawn from SIO pin 10 (+5V/Ready)
- User's documentation: C026119 (1985) Atari XM301 Modem
- Field service manual: ?????
Atari SX212 Modem
- Type: Direct-connect modem
- Speed: 75-300 and up to 1200 bit/s
- Compatibility: Bell 103/113/212A modem compatible (U.S. industry standards)
- Compatibility: Hayes command set compatible
- Incompatibilities: With an 800XL, cannot be used with a tape recorder
(reason unknown?????). The manual reads "If you are connecting your SX212
modem to an Atari 800XL computer, you cannot operate the modem and a
cassette recorder at the same time. Remove the recorder before using the
modem."
- Additional hardware requirement: (none)
- Connectivity: - Atari SIO (must be at end of of SIO chain)
- Uses SIO Motor Control; only one such device can be
attached to the system at a time.
- DB-25S RS-232 serial
- Key engineer/designer: Jose Valdes at Atari
- Made in Taiwan
- Built-in speaker with adjustable volume for call monitoring
- Auto-dial and auto-answer capabilities
- Operation: Full duplex and half duplex
- Dialing capabilities: Tone and pulse (rotary) dialing
- Carrier frequencies
- 1200 bit/s; Originate; Transmit 1200Hz, Receive 2400Hz
- 1200 bit/s; Answer; Transmit 2400Hz, Receive 1200Hz
- 75-300 baud; Originate; Mark 1270Hz, Space 1070Hz
- 75-300 baud; Answer; Mark 2225Hz, Space 2025Hz
- Receive signal frequency tolerance: +/- 7Hz
- Bit error rate: Less than 1 in 10E5 bits for signal-to-noise ratio of 8dB
with 300Hz to 3400Hz Gaussian noise over a receive level range of -10dBm to
-35dBm
- Loss of carrier: Disconnects automatically in 1 +/- 1 second after loss of
carrier
- Command buffer: 40-character command buffer
- Receiver sensitivity: -40dBm
- Transmit level: -9dBm
- SX Express! sold separately (DX5089)
- Package includes Program Disk, User's Manual, and SIO cable
- SX Express! Program Disk (DX5089) includes:
DOS.SYS DOS 2.5 File Management Subsystem (FMS)
DUP.SYS DOS 2.5 Disk Utility Package (DUP)
AUTORUN.SYS SX Express! Ver. 3.00 by Keith Ledbetter
RAMDISK.COM DOS 2.5 130XE RAMdisk utility
HANDLER.OBJ R: device handler (by Paul Swanson)
HANDLER.DOC SX212 Modem Handler Technical Description
- Power: External 500mA 9V DC (center positive). Shipped with Atari C016353.
- User's documentation: (1987) C070878 (CO70878) C033506 (CO33506)
Atari SX212 Modem - Owner's manual
- Field service manual: ????? |