Freedom
~~~~~~~
Freedom Issue 2, February 28, 1993
File 1/7
Introduction
~~~~~~~~~~~~
Welcome to issue 2 of Freedom, thanks to everyone who submitted to
the first issue, and this one. I'll keep this intro short, since I don't have
much to say.
There's been a new section added which i've called Tidbits, that
basically consists of small articles that weren't appropriate to put in
separately. If you have something that you feel isn't worth writing a full
fledged article on, it can be included in this section.
If you would like to submit an article, or get a hold of me, either
call one of the boards listed hereafter or send it via internet e-mail to
[email protected].
Freedom can be found on
Silicon Valley 2o4.669.7983
as well as the following systems:
Unphamiliar Territory 6o2.894.1757
The Phrozen Realm 514.738.21o5
ICEMAN
[email protected]
Index
~~~~~
I. Introduction by ICEMAN.
II. Northern Telecom SL-1's by ICEMAN.
III. How to reduce taxes, eliminate welfare, and reduce organ donor shortages
at no cost to honest hardworking individuals by Vox Populii.
IV. Computers and Radios by Illusion.
V. The Invisible Answering Machine by Lazarus Long.
VI. Catalog Reviews by Lazarus Long.
VII. Tidbits.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Freedom Issue 2, February 28, 1993
File 2/7
Northern Telecom SL-1
by ICEMAN
This article is fairly lengthy, but I felt that it was worth including
all the information that I did, even though a great deal of it is useless to
someone attempting to take advantage of such a system. If you have any
interest in learning about PBX's, then in my opinion it's worth reading in
it's entirety. Just a note that you can't expect to learn this all in one
sitting, it takes time and experience. I would say that about 50% of this
material was taken from other sources, ranging from Northern Telecom manuals,
to classroom handouts used to educate those who work with them. Although most
of the technical information is straight out of the book, I did my best to
simplify it as much as I could, so that the reader can get a better grasp on
it.
Development of Northern Electric's SL-1 started in 1971. Their
objective was to design a superior communications system for business
subscribers in the range of 100 to 7600 stations. The system had to encompass
all the features of a PBX, Centrex and key systems and be economically
competitive with them. It had to have new custom services not previously
feasible with the older systems. It had to be easy to learn and to operate.
As well, it had to be easy to install and maintain.
What the designers came up with was a digital, stored program control
machine using an 8-bit PCM. They also came up with a new telephone instrument,
the SL-1 telephone, which is a multi-line instrument with many features, but
uses only 2 pairs of wires, instead of 25 pairs required by key telephones.
The SL-1 system has three main parts: The common equipment (CE), the
peripheral equipment (PE) and the power supplies.
The CE performs the central control and switching functions for all
the connecting lines and trunks. It has a central processing unit (CPU) and
read/write memory which stores all the operating programs and data unique
to the particular system, including switching sequences, feature and class
of service information, and numbers and types of terminals. It also has a
magnetic tape unit for high-speed loading of the operating programs and data
into the R/W memory, providing data restoral after a power failure. The tape
also contains the diagnostic routines. There is a Teletype to communicate to
the system with and to print error messages on. The network circuits perform
the switching duties for all lines and trunks. The digital service circuits
provide for such functions as dial and ringing tones and call conferencing.
The CE units communicate over a common central bus under control of
the CPU. Speech signals, converted to digital, follow a separate path on a
network switching bus.
The PE performs the interface between the line and trunk circuits and
the SL-1 system. It consists mainly of line and trunk cards which convert
analog speech to digital signals for digital switching and vice versa. Lines
connect to individual instruments and trunks to other PBX's. Peripheral
buffers act as interface between the PE and the CE providing power control,
timing and switching control signals for the line and trunk circuits. Digital
conversion into 8-bit PCM is done by a single encoder/decoder (codec) for each
line or trunk. This codec is a custom LSI circuit.
Between the PE and the CE, all signals travel in digital format on
time multiplexed loops. Each loops carriers 30 voice channels, one control
signalling channel and one unused channel. The channels operate at 64 kbps
to give a total data rate of 2.048 mbps. Each loops terminates on a different
circuit pack in the CE. There can be up to 16 multiplex loops.
When a call is set up, the CPU assigns each party a channel from among
the 30 on their own multiplex loops. These channels form a matched pair. For
instance, the calling party may use channel 2 of it's digital loop, and the
called party may use channel 3 of it's loop.
The SL-1 conducts audio digitally. The line and trunk cards contain
A/D and D/A converters. Received audio is changed to a digital signal and
put on a voice channel. At it's destination, the digital signal is converted
back to analog audio.
All programming is done from a keyboard with the output going to a
printer. To program, a specific diagnostic is selected, and is automatically
loaded from tape. Once this is done, the appropriate commands are entered to
change the options. All typing is echoed on the printer and the SL-1's
responses are printed out. If any system parameters or configurations are
changed, these changes will not survive a total power outage unless a new
tape is made.
In case of a power outage, upon restoral of power, the SL-1 activates
the tape unit and loads in the system operating data, and runs some
diagnostics. This takes from 5-15 minutes, and at the end of that time,
service is fully restored with all the options which were recorded on the tape
being implemented. Of course any user-selected options like speed call lists
and call waiting which had been selected before the outage will be lost.
Automatic diagnostics (called 'background' programs) are being run
constantly with the results of any problems being printed out. At midnight
a more thorough set of diagnostics are run. Any of the diagnostics may be
run on demand from the keyboard. Also available on demand from the keyboard
are a series of diagnostics to determine the status of lines and trunks, to
trace calls, and to print lists and traffic studies.
SL-1 Features
~~~~~~~~~~~~~
- Call Waiting - Digitone (DTMF) service
- Ring Again - Direct inward dialing
- Display services - Direct outward dialing
- Tandem switching - Private line service
- Special dial tone - Remote administration and
- Traffic measurement maintenance
- Common control switching - Multi-customer group operation
arrangement access - Line/trunk lockout
- Data transmission - Flexible numbering system
- Access to automatic recorded (2 to 4 digits)
answering equipment - Pulse to DTMF conversion
- Access to paging equipment - DTMF to pulse conversion
- Call forward - busy - Emergency transfer
- Call forward - don't answer - Hunting
- Call forward - follow me - Intercept
- Call pickup - Manual service
- Conference (3 or 6 party) - Night service
- Service restrictions
SL-1 Telephone Set Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Autodial - Automatic preselection
- Call status - Headset connection
- Call forwarding - Executive override
- Call transfer - Hold
- Speed calling - On-hook dialing
- Call waiting - LED indicators
- Tone ringing - Call pickup
- Common audible signalling - Loudspeaker/Amplifier
- Ring again - Voice calling
- Hands free operation - Manual signalling
- Multiple appearance directory - 3 or 6 party conference
number; multiple call - non-locking keys
arrangements - Single appearance directory
- Prime directory number number
- Station set expansion - Privacy
- Privacy release
Explanation of Some Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Station to station calling - Any station can directly call any other station
without attendant assistance.
Direct Outward Dialing (DOD) - Allows a station to gain access to the exchange
network without attendant assistance and receives a second dialtone.
Hunting - Routes a call to an idle station directory number when the called
number is busy. The numbers in the hunt group do not have to be in sequence
nor do they have to appear on the same instrument. The sequence can be
consecutive (station directory numbers are hunted in ascending numerical
order) or non-consecutive.
Access to paging - Provides a connection to customer-owned paging equipment.
Access to Automatic Recorded Answering Equipment - SL-1 stations can have
incoming messages recorded on customer-provided answering equipment by
forwarding calls to the directory number (DN) assigned to the equipment.
Direct Inward Dialing (DID) - Allows an incoming call from the exchange
network to reach a station without attendant assistance. The DN for each
station will normally be the last 2,3 or 4 digits of the 7 digit exchange
network number.
Tandem Switching - The SL-1 can act as an intermediate switching point for
traffic between other PBX's.
Manual Service - Does not provide a dialtone when a station goes off-hook.
Instead the attendant is alerted and completes the call for the user.
Private Line Service - Permits the appearance of a private central office line
on an SL-1 Telephone set. Dialtone is received directly from the telco and
calls are not processed by the SL-1.
Multi-Customer Group Operation - Allows for the provision of services for more
than one business customer from the same switching machine. Each customer
is totally separate from the others, may have the same directory numbers as
the others, has his own attendant console, his own trunks, and cannot directly
call stations belonging to the other customers.
Service Restrictions - Allows the ability to restrict various functions.
Intercept - Disposes of calls which cannot be completed because of
restrictions or dialing errors. They are either routed to the attendant
or overflow tone.
Special Dial Tone - A Regular dialtone with three 128 ms interruptions at the
beginning to advise the user that his hookswitch flash has been successful.
Line Lockout - Disconnects stations which have been off-hook for too long to
prevent system problems.
Night Service - Allows the attendant to preconnect some or all of the incoming
telco trunks to selected DN's on the SL-1.
Emergency Transfer - Puts the system in the power fail transfer mode. This
transfers telco trunks to selected stations to provide some continuity of
service to the outside world during the time the SL-1 is inoperative.
Remote Administration and Maintenance - Permits operation of the diagnostics
from a remote location via a modem and telephone line. You may do anything
from the remote terminal that you can do from the local terminal.
Call Forward - Busy - Routes incoming calls to another number when the called
station is busy.
Call Forward - Don't answer - Routes incoming calls to another number when the
called station doesn't answer within a prescribed time.
Call Forward - Follow me - Routes incoming calls to another, programmable
number.
Call Waiting - Informs the user of a second incoming call while he is already
in conversation. He can then place the first caller on hold and answer the
second call. He can then return to the first call.
Conference - Allows a user to connect up to either 1 or 4 additional persons
into an existing call. Up to 2 of the users may be trunks.
Call Pickup - Allows a station to answer an incoming call to another station
in the same pickup group by dialing a special code.
Ring Again - Permits a calling station, on encountering a busy DN, to operate
a dedicated key or dial a special code to have the system monitor the called
station and alert him when it goes idle. He is then automatically connect to
that station when he goes off-hook or presses the key during the alert and the
system rings that station.
Data Transmission - The SL-1 is suitable for voiceband data transmissions
and is compatible with a conventional modem.
SL-1 Models
~~~~~~~~~~~
Model Lines Introduced Generic Features
~~~~~ ~~~~~ ~~~~~~~~~~ ~~~~~~~ ~~~~~~~~
SL1-L 300-700 1975 x01 - N/A
SL1-VL 700-2500 1976 x02 - Multi customer operation
- Automatic Identification of
outward dialing
- Do not disturb
CDR N/A 1977 x03,x04, - Call detail recording
x08 - Recorded Announcement
- Digit display console
SL1-LE 300-700 1978 x05 - Automatic Route Selection
SL1-VLE 700-2500 N/A N/A - Remote peripheral equipment
- Automatic Number Identification
- "E" system
- Autovon
SL1-A 60-400 1979 x06,x07, - Centralized attendant service
x14 - Automatic call distribution
- Digit display SL-1 Sets
- 2500 Set Features
- Direct inward system access
- Dial Intercom
- Message Center
- Hotel/Motel
- International Phase 1
SL1-XL 1000-5000 1980 x09,X17 - Advanced ACD packages
- Multiple message center
- Integrated voice and data
switching
- Hospital/Clinic
- International Phase 2
ESN N/A 1981 x9000 - Office data administration
system
- Automatic Wake-up
- Room status
- Auxiliary data system
- Electronic switched network
- International Phase 3
SL1-M 60-400 1982 x11 rls 1 - Attendant Administration
- Attendant overflow
- Automatic set relocation
- History file
- Call park
- Flexible code restriction
- System speed call
- International Phase 4&5
SL1-S 30-160 1983 x11 rls 4 - Distinctive ringing
- Stored number redial
- Async. interface module
- Sync. data transmission
- Multi-channel data system
- SL-1 displayphone
- Hotel/Motel
'Generic' refers to the software version. It is expressed as a 3 or 4 digit
number where the first part of the number indicates the machine it is for
and the second part indicates the purpose of the software and serves as a
version number and also indicates the type of machine it can be used with. The
'X' stands for a 1 or 2 digit number representing the model:
1 = SL1-L 2 = SL1-VL 3 = SL1-LE 4 = SL1-VLE 5 = SL1-A
6 = SL1-XL 7 = SL1-M/S 8 = SL1-N 9 = SL1-XN 10= SL1-ST
11= SL1-NT 12= SL1-XT
Maintenance Programs
~~~~~~~~~~~~~~~~~~~~
All troubleshooting procedures, configuration changes and circuit
disabling/enabling are carried out from the keyboard of a Teletype via
software programs. There is virtually no physical contact with the exchange
other than required to remove a defective board and replace it with a spare.
Even this does not require tools.
This material will give only a brief description of each program and
some examples of how to use them.
Before running a program you must first gain access to the computer.
The dialup will normally be a 1200 baud connection, with an even parity,
databits of 7, and stopbits of 1 (E71). Once connected press the 'return'
key to wake the system up. The system SHOULD respond with 'OVL111 BKGD' or
'OVL111 IDLE' and now you know it's alright to login. If the response is
'OVL000' and then a '>' prompt you are already logged in, and you can go
straight to loading an overlay.
Type 'LOGI' to initiate the login. Make sure when entering commands
that they are all input in uppercase. The system responds with 'PASS?'. Now
enter the password. The default password is '0000' but is obviously
configurable. If you have correctly logged in, the system will respond with
a '>' prompt. The system will display this prompt whenever waiting for
operator input and is not running a diagnostic program. Once a diagnostic
program is running the prompt becomes a '.' (period). If you are not logged
in, there is no prompt.
What follows is an example of what you will see during login.
{ Hit Carriage Return }
