Electronic Mail Systems: Communication Networks For Libraries
| DOI | https://doi.org/10.1108/eb047479 |
| Pages | 41-43 |
| Date | 01 January 1983 |
| Published date | 01 January 1983 |
| Author | Libby Trudell |
| Subject Matter | Information & knowledge management,Library & information science |
Electronic Mail Systems:
Communication Networks For Libraries
LIBBY TRUDELL
The term "Electronic Mail System," or EMS,
has many different definitions. In introducing this
topic which will be a regular feature of LHT, it is use-
ful to define the scope of that term, at least enough
to give readers some idea of what to expect.
What is electronic mail? A recent article about
EMS in Today's Office quotes Louis M. Galie, Direc-
tor of Office Workstation Engineering of Burroughs
Corporation, defining it as "the electronic transmis-
sion of messages, text, and graphics between two or
more individuals." In terms of this definition, elec-
tronic mail is a pretty broad topic, encompassing
TWX and Telex, facsimile, communicating word
processors and microcomputers, and host computer
message systems. Certainly there is a lot of scope for
review here.
On the other end of the scale, many people use
the term EMS only for computer-based message sys-
tems.
EMS systems such as OnTyme or The Source,
where messages are stored in the host computer for
later retrieval, are commonly known examples.
For this column, I propose a definition of EMS
which falls somewhere in the middle: EMS is the
transmission of messages or text in digital format
from one computer terminal to another. This defini-
tion leaves us on hazy ground for the inclusion of
teletype networks such as TWX and Telex, where
text is transmitted in a five-bit baudot code (incom-
patible with most computer terminals) as opposed to
seven-bit ASCII code. However, the development of
interface devices which translate from one code to
other other, so that the user is aware only of lovely
alphabetic characters being printed out at either end,
means that teletype should probably be considered
part of the family.
Within this broad definition, EMS can be divided
into two basic types. One type is a message network
in which messages are sent directly from one terminal
to another. The functions of text creation, transmis-
sion, message receipt and storage are handled locally
at each node in the message network. In such a net-
work, each terminal must be equipped with enough
intelligence to handle these functions.
This type of node-to-node network can be con-
trasted with a computer-based message system
(CBMS). With a CBMS, any dumb terminal can be
used to access the host computer which acts as a de-
pository for all messages and holds them until the
recipients log on to the computer and read the mail.
Node-to-Node Networks
As the name implies, data transfer in a node-to-
node network occurs directly between two points or
"nodes"
in a communication network. Like the famil-
iar telephone answering machine, the basic require-
ments at each node are an auto-answer modem that
answers the call and also a device to print out or dis-
play the messages. Each node must have the capa-
bility to compose and store the actual text to be
transmitted built into the terminal or in a peripheral
device. With this kind of equipment, data can be
transmitted from node to node just by dialing up over
regular phone lines.
If messages can be sent by making a local phone
call, the cost of the transmission is minimal. Using
Telco lines means rapid increase in cost as the dis-
tances between nodes increases. For this reason, node-
to-node communication is generally best for local
networking applications. However, it is possible to
use equipment which can be set up to transmit at a
designated time without operator assistance. In this
way late night phone rates can be used to significant-
ly lower long distance costs.
Another advantage of this type of configuration
is that messages are received as soon as they are trans-
mitted. However, if one call is in progress, no other
call can get through until it ends and message trans-
mission can be delayed because the lines are busy
when the call is placed. Auto-dial devices that retry
automatically can alleviate this problem.
Such networks are limited by the fact that a
separate call must be placed to each message recipi-
ent. And, since the equipment must be ready to re-
ceive messages at all times, the terminal cannot easily
be used for other online activities.
Trudell is Coordinator for Online Systems for
the California Authority for Systems and Services and
Assistant Editor of LHT, responsible for Electronic
Mail and Facsimile Transmission.
SUMMER 1983 41
To continue reading
Request your trial