Modems and external dialers.

[allison]

On 06/05/2019 12:01 PM, Electronics Plus via cctalk wrote:
> 
> 
> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Grant Taylor via cctalk
> Sent: Wednesday, June 05, 2019 10:42 AM
> To: cctalk at classiccmp.org
> Subject: Re: Modems and external dialers.
> 
> On 6/4/19 8:30 PM, allison via cctalk wrote:
>> Keep in mins the hardware for auto dial required some for of micro and 
>> that was a post 1974 thing for the most part.
> 
> Why did it require a micro?  Could the host not perform the function 
> that the micro would do?
> 
>> A few before that had a lot of TTL state machine to do that. 
>> They obviously weren't cheap.

Simple answer was at that time micros were not yet invented.  Actually
they were but not economical when a 8080 board or 6502 board required a
large handful of parts.  Before that? Whats an 8080?


> Why did that state machine need to be implemented in electronics?

It was a way to have rudimentary smarts that was not quite a cpu.

> Why couldn't that state machine be implemented in software on the host 
> using the modem & auto-dialer?
>

IT was the auto dialer!  OR it used manual dialer.


>> The dialer was often not at all as it was the human that dialed the phone.
> 
> ~chuckle~
> 
>> I know of none that did both functions that required a second serial port.
> 
> Okay.
> 
> Reading the links that Ethan provided, it sounds like some auto-dialers 
> did use a second port, but it was not a second (recommended) standard 
> 232 port.  Instead it was an RS-232 and RS-366.
> 
> Aside:  RS-366 sounds odd.  A combination of serial signaling and 
> parallel signaling on the same port.  But not the same as a traditional 
> parallel printer port.
>

Those likely existed but it was for system that did a lot of dialing out.

>> My first modem was a box about 12x8x2.5 inches and it was an all analog 
>> modem good for 110/300 baud and it required connection to the phone line 
>> (pre-modular connector) and you dialed the various (and relatively scarce) 
>> BBSs and when you heard the tone hit the switch that put the modem on 
>> the phone line and you would see the carrier and data lamps do their 
>> thing. That was 1978ish.
> 
> Aside:  I assume that you're talking about before the small 6-position 2 
> or 4 conductor plugs.  Or are you referring to the older than that 
> not-quite-square 4 pin plug?  Or was the modem actually hard wired in 
> with no plug / jack at all?

For a lot of years the older hardware TELCO had ws still in place.
I still have a 500 series deskset and it works well!  So at that time
I connected using whatever ways needed, sometimes I upgraded to makes it
easier next time.

Modular is the RJ stuff newer and still in use, the older was the
larger clunky 4 pin plug.  My house still has a few.


>> A modem that could dial was maybe 1983-5 or so at affordable prices 
>> (under 300$) for 300 baud.
> 
> *nod*
> 
> I have this mental picture, which I think is based on something I've 
> seen at some point in the past, that was a device that attached / 
> actuated / ??? a traditional rotary dial phone.  As in it had a finger 
> that interfaced with the dial and something that could rotate it to dial 
> the digit in question, rewind (term?), and dial the next digit in question.
> 

Wild idea but never saw that one.  I have the advantage of spanning
computing from late 60s to now.  The intersting case was 1970, PDP10
with PDP8I the 8I did all the communications between the 10 (blkio)
and the modem bank which was dial in only.  Over 300 users on the BOCES
LIRICS computer network and 98% of them were ASR33 with 110baud
acoustic coupled modem.  the last 2% were ASR35 and Hazeltine 1000 and
2000 terminals in the center (local 1200baud!).

So I remember pre-carterphone to 56K modems, then DSL and now fiber.
My memory of carterphone was a interconnect for radios (Amateur radio)
and how we then just did it being very careful with transformer
isolation.  By 1970 I was working in the land mobile industry with
remote base radios connected with RTL (Radio Tie Lines) which were just
a pair of rented wires (owned by TPC aka telco) between the business to
the hill where the radios were.  They had to pass DC and every so often
some bright eyes would add load coils and effectively short out the
line.  That would cause a day of troubleshooting as it was never the
TPCs fault.  At least according to them.

Allison