TELECOM@Usc-Eclb.ARPA (04/20/83)
TELECOM AM Digest Wednesday, 20 April 1983 Volume 3 : Issue 27
Today's Topics:
Calling Cards For International Calls
Hands-Free Telephony
Portable terminals
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Date: 17 Apr 1983 at 1103-PST (Sunday)
From: tekecs!stevenm.Tektronix@Rand-Relay
Return-Path: <tekecs!stevenm.tektronix@rand-relay>
Re: calling cards for international calls
I agree with the sentiment that charges for calling cards for
international calls should be normalized, but I own and use a calling
card anyway. I have found it essential for overseas use. The reasons
are as follows:
1) Many (most) countries have phone systems which are
extremely primitive in comparison to ours;
2) Additionally, phones are not as widely available in some
countries as in America.
3) Many countries will not accept reverse-charged calls
These factors conspire, in many countries (eg. Ireland, where I
traveled most recently) to make long distance calls from somewhere
other than a fairly fancy hotel impossible. Staying at phone-less Bed
& Breakfast places in Ireland, I was forced to use pay phones
(typically in taverns) for my long distance calling. I placed a call,
and then had a few pints waiting for the operator to put it through.
The hitch is that if I hadn't had the calling card, I would have had
to put about $20 (uh, 12 pounds or so) in the phone in 5 pence pieces.
Because of limitations on the size of the coin boxes on these phones,
that, of course, was impossible.
S. McGeady
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Date: Mon Apr 18 10:15:56 1983
From: harpo!hou2b!dvorak@UCB-VAX
Subject: HANDS-FREE TELEPHONY
There has been a fair amount of inaccurate information appearing here
with regards to devices permitting hands-free audio. Note that in the
comments that follow, headsets are not included; rather, hands-free
audio pertains to a telephonic 'terminal' that has a microphone and a
speaker that anyone nearby can use.
For example, consider the traditional speakerphone. It is
voice-switched, which basically means that when it transmits, incoming
signals are essentially blocked. This feature is necessary to prevent
talker 1 from having his voice broadcast in talker 2's room, only to
be picked up by talker 2's mike and fed back to talker 1. Think of it
as a half-duplex device as compared to the full-duplex properties of
two talkers each using handsets: No voice-switching, so you can talk
and listen simultaneously. More importantly, you can interrupt the
other person--which is the way in which real people communicate. But
with a speakerphone, when you can hear the person talking from a
speakerphone, then you know he cannot hear you. Supervisory personnel
here at the Labs routinely use these devices, although it is unclear
whether it is (a) to indicate their status, (b) have their hands free,
(c) to be the live side of a half-duplex channel, or (d) all of the
above.
The 'rain-barrel' effect one gets when listening to someone on a
speakerphone is due to the reverbations within the room of the
speakerphone. It is echo, but multiple relections of short duration.
No practical technology exists to correct it other than acoustically
treating the room.
Which brings up the Quorum (TM) Mike, a linear array of mikes in a
vertical stalk that overcomes the hypersensitivity of other systems to
the dependence of volume level on the distance of the speaker from the
mike. It's neat--a conference room full of people sit and speak at
natural levels no matter where they are relative to the mike. The
receiving station hears a fairly uniform level.
But it is NOT the case that the 'echo' problem is solved. The device
is still voice-switched, and acoustic treatment is necessary to avoid
lots of reverb. The high price ($1700 was quoted here last week) is
testimony to the fact that it is intended for business/educational use
by rooms full of people who choose to teleconference rather than
travel.
Hope this all was of some help in clearing the air.
--Chuck Dvorak (floyd!hou2b!dvorak)
Bell Labs, Holmdel
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Date: Monday, 11 April 1983 14:17-EST
From: Marvin Sirbu <SIRBU at MIT-XX>
Re: Portable terminals
The annual report of Motorola contains this note of interest:
[Motorola] has developed a unique land-mobile radio/data
communications system which gives users access to computers while on
the move. The basic element of the system is a handheld computer/data
terminal containing both a radio and a telephone modem. The system's
intelligent network controller directs messages between a large fixed
computer and the portable user, and controls the operation of the
radio network.
The portable computer/terminal ... features read-only and random
access storage, a two-line liquid crystal display, and an alphanumeric
keyboard...
The first customer, IBM has contracted for a system to be used by its
field service personnel. The IBM system will consist of approximately
250 separate citywide radio networks, coordinated by 20 intelligent
network controllers, each interfacing with the IBM nationwide computer
network. Each controller is capable of supporting up to 1,500
portable users. Installation will begin in late 1983 and is scheduled
for completion in 1985.
The article doesn't say whether packet radio or some other technique
is being used to control access.
Coupled with the recent FCC decision to liberalize the use of SCA's,
we may see even more of this kind of thing.
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End of TELECOM Digest
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