POTS line quality help [Design]

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From: JosephKK on 4 May 2010 00:10

On Sun, 02 May 2010 20:13:16 -0700, Robert Baer <robertbaer(a)localnet.com>
wrote:

>Robert Baer wrote:
>> Robert Baer wrote:
>>> Robert Baer wrote:
>>>> denali wrote:
<snip>
>>>> I presume you reviewed the two ascii files attached elsewhere; i
>>>> made a third try with a differrnt setting S0=1, S32=2 and the modem
>>>> indicated speed 45333/26400 with protocol LAPM/SREJ (whatever that
>>>> means).
>>>> So i went into dial-up networking and changed the initialization
>>>> string for that.
>>>> The little double-monitor icon now indicates 48K which is a decided
>>>> improvement.
>>>> Any way i can goose it more?
>>> I tried initialization string S0=1 S32=96 and connection was
>>> refused; setting back (no reboot) to S0=1 S32=2 gives connection and
>>> 48K rate.
>> To see if i could control the data rate, i tried "z s0=1 s32=2 &n38"
>> for initialization string (force 56K) and nogo; then "z s0=1 s32=2 &n36"
>> and got 48K (supposed to force 53.3K), then "z s0=1 s32=2 &n17" and
>> still got 48K (supposed to force 28K).
>> So i dropped the &n and am using "z s0=1 s32=2" for now.
> Do not understand the modem response speed 45333/26400 but discovered
>that download rate can be extremely slow IF IT EXISTS AT ALL, so i
>reverted to the standby "S0=0 S23=98" even tho that gives me 28.8K at
>best; it works in both directions.
> Suggestions for consistent 48K both directions?

I had somewhat misinterpreted your goal. Try S33=15 and S34=7.

From: Robert Baer on 4 May 2010 03:00

JosephKK wrote:
> On Sun, 02 May 2010 20:13:16 -0700, Robert Baer <robertbaer(a)localnet.com>
> wrote:
>
>> Robert Baer wrote:
>>> Robert Baer wrote:
>>>> Robert Baer wrote:
>>>>> denali wrote:
> <snip>
>>>>> I presume you reviewed the two ascii files attached elsewhere; i
>>>>> made a third try with a differrnt setting S0=1, S32=2 and the modem
>>>>> indicated speed 45333/26400 with protocol LAPM/SREJ (whatever that
>>>>> means).
>>>>> So i went into dial-up networking and changed the initialization
>>>>> string for that.
>>>>> The little double-monitor icon now indicates 48K which is a decided
>>>>> improvement.
>>>>> Any way i can goose it more?
>>>> I tried initialization string S0=1 S32=96 and connection was
>>>> refused; setting back (no reboot) to S0=1 S32=2 gives connection and
>>>> 48K rate.
>>> To see if i could control the data rate, i tried "z s0=1 s32=2 &n38"
>>> for initialization string (force 56K) and nogo; then "z s0=1 s32=2 &n36"
>>> and got 48K (supposed to force 53.3K), then "z s0=1 s32=2 &n17" and
>>> still got 48K (supposed to force 28K).
>>> So i dropped the &n and am using "z s0=1 s32=2" for now.
>> Do not understand the modem response speed 45333/26400 but discovered
>> that download rate can be extremely slow IF IT EXISTS AT ALL, so i
>> reverted to the standby "S0=0 S23=98" even tho that gives me 28.8K at
>> best; it works in both directions.
>> Suggestions for consistent 48K both directions?
>
> I had somewhat misinterpreted your goal. Try S33=15 and S34=7.
S33 V.34 & V.34+ Connection setup bit mapped control flags.
1 = Disable 2400 Symbol rate
2 = Disable 2743 Symbol
4 = Disable 2800 Symbol rate
8 = Disable 3000 Symbol rate
A setting of 15 would disable all of these.
S34 V.34 & V.34+ Connection setup bit mapped control flags.
1 = Disable 8S-2D trellis encoding
2 = Disable 16S-4D trellis encoding
4 = Disable 32S-2D trellis encoding
A setting of 7 would disable all of these.
Will try.

From: Martin Brown on 4 May 2010 04:13

Robert Baer wrote:
> Martin Brown wrote:
>> Robert Baer wrote:
>>> Robert Baer wrote:
>>>> I presume you reviewed the two ascii files attached elsewhere; i
>>>> made a third try with a differrnt setting S0=1, S32=2 and the modem
>>>> indicated speed 45333/26400 with protocol LAPM/SREJ (whatever that
>>>> means).
>>>> So i went into dial-up networking and changed the initialization
>>>> string for that.
>>>> The little double-monitor icon now indicates 48K which is a
>>>> decided improvement.
>>>> Any way i can goose it more?
>>> I tried initialization string S0=1 S32=96 and connection was
>>> refused; setting back (no reboot) to S0=1 S32=2 gives connection and
>>> 48K rate.
>>
>> Changing the xon character to 96 = 0x60 = ' is unlikely to be helpful.
>> Where did you get the idea that this would be sensible?
>>
>> Default is S32=17 and it would only be relevant if you were on a poxy
>> three wire serial link without hardware handshaking. This is extremely
>> unlikely for an internal modem. Typically they have a much larger FIFO
>> than standard serial port chipsets and fullspeed hardware handshaking.
>>
>> I strongly suggest that your problems here are largely self inflicted.
>>
>> Do AT&V0 and capture the result it displays. Posting that here will
>> give us a sporting chance of undoing the mess you have got yourself into.
>>
>> Your best bet now is to reset the modem to its factory defaults
>> (usually two variants one is robust and the other tries to be
>> go-faster). Try each one of these in turn and you might actually get
>> somewhere useful.
>>
>> AT&F
>> AT&F0
>> AT&F1
>>
>> Several of the other S registers you have meddled with are either
>> reserved or undocumented or typos in your report of what you did.
>>
>> When you get it right store the best profile with AT&W0
>> Then initialise your modem with ATZ0
>>
>> Regards,
>> Martin Brown
> All of the following commands result in ERROR : AT&V0 , AT&F , AT&F0
> and AT&F1.

Try AT&V or ATI4 then. Something is very fishy here...

You should be able to make the modem tell you what its settings are.

> I did not change any character, XON or otherwise.
> S32=17 would disable V.34+ (value 16) and enable v.8 indicate (value
> 1) and certainly would not enable v.8 mode (value 2).

Where did you get this information?
Most of the rest of the world uses different numbered S registers eg.

http://www.arcelect.com/MIU96-144_%20AT_Command_Set_and_S-Registers_0049-0002-005A.pdf

S32 is the Xon character (changing it not implemented in some modems).
I was also suspicious of your &N17 but put it down to careless typos.
Something which incidentally does not bode well for setting S registers.

> I have an external modem; refuse to use an internal of any type as i
> can SEE the lights on an external modem and have a fair idea as to which
> way data is traveling (and how much).

You are completely barking. Have you even got a decent FIFO buffered
16550 type serial card in this derelict PC ?

A PC of the implied vintage to be running Win98 basic serial ports
cannot keep up with the modem adequately at 56k speeds without having a
FIFO to absorb the slack. Dropped characters force retransmits and slows
things down. If you use an internal modem the FIFO is much bigger.

Regards,
Martin Brown

From: Robert Baer on 4 May 2010 23:43

Martin Brown wrote:
> Robert Baer wrote:
>> Martin Brown wrote:
>>> Robert Baer wrote:
>>>> Robert Baer wrote:
>>>>> I presume you reviewed the two ascii files attached elsewhere; i
>>>>> made a third try with a differrnt setting S0=1, S32=2 and the modem
>>>>> indicated speed 45333/26400 with protocol LAPM/SREJ (whatever that
>>>>> means).
>>>>> So i went into dial-up networking and changed the initialization
>>>>> string for that.
>>>>> The little double-monitor icon now indicates 48K which is a
>>>>> decided improvement.
>>>>> Any way i can goose it more?
>>>> I tried initialization string S0=1 S32=96 and connection was
>>>> refused; setting back (no reboot) to S0=1 S32=2 gives connection and
>>>> 48K rate.
>>>
>>> Changing the xon character to 96 = 0x60 = ' is unlikely to be helpful.
>>> Where did you get the idea that this would be sensible?
>>>
>>> Default is S32=17 and it would only be relevant if you were on a poxy
>>> three wire serial link without hardware handshaking. This is
>>> extremely unlikely for an internal modem. Typically they have a much
>>> larger FIFO than standard serial port chipsets and fullspeed hardware
>>> handshaking.
>>>
>>> I strongly suggest that your problems here are largely self inflicted.
>>>
>>> Do AT&V0 and capture the result it displays. Posting that here will
>>> give us a sporting chance of undoing the mess you have got yourself
>>> into.
>>>
>>> Your best bet now is to reset the modem to its factory defaults
>>> (usually two variants one is robust and the other tries to be
>>> go-faster). Try each one of these in turn and you might actually get
>>> somewhere useful.
>>>
>>> AT&F
>>> AT&F0
>>> AT&F1
>>>
>>> Several of the other S registers you have meddled with are either
>>> reserved or undocumented or typos in your report of what you did.
>>>
>>> When you get it right store the best profile with AT&W0
>>> Then initialise your modem with ATZ0
>>>
>>> Regards,
>>> Martin Brown
>> All of the following commands result in ERROR : AT&V0 , AT&F , AT&F0
>> and AT&F1.
>
> Try AT&V or ATI4 then. Something is very fishy here...
>
> You should be able to make the modem tell you what its settings are.
>
>> I did not change any character, XON or otherwise.
>> S32=17 would disable V.34+ (value 16) and enable v.8 indicate (value
>> 1) and certainly would not enable v.8 mode (value 2).
>
> Where did you get this information?
> Most of the rest of the world uses different numbered S registers eg.
>
> http://www.arcelect.com/MIU96-144_%20AT_Command_Set_and_S-Registers_0049-0002-005A.pdf
>
>
> S32 is the Xon character (changing it not implemented in some modems).
> I was also suspicious of your &N17 but put it down to careless typos.
> Something which incidentally does not bode well for setting S registers.
>
>> I have an external modem; refuse to use an internal of any type as
>> i can SEE the lights on an external modem and have a fair idea as to
>> which way data is traveling (and how much).
>
> You are completely barking. Have you even got a decent FIFO buffered
> 16550 type serial card in this derelict PC ?
>
> A PC of the implied vintage to be running Win98 basic serial ports
> cannot keep up with the modem adequately at 56k speeds without having a
> FIFO to absorb the slack. Dropped characters force retransmits and slows
> things down. If you use an internal modem the FIFO is much bigger.
>
> Regards,
> Martin Brown
The FIFO *is* a decent FIFO buffered 16550 type "serial card"
emulated in the PCs ASIC; ASUS M2N-MX SE Plus clock 2700Mhz.
Your "S" register descriptions are cattywhumpus with regard to
Rockwell which is one of the standards - that BTW follows Hayes, another
standard.
AFAIK US Robotics used a Rockwell chip; cannot tear into it right
now(!!).

Copy and paste of manual session; note S register info *directly*
from modem:
ATE1
OK
ATI4
U.S. Robotics 56K FAX EXT Settings...

B0 E1 F1 M1 Q0 V1 X4 Y0
BAUD=115200 PARITY=N WORDLEN=8
DIAL=TONE ON HOOK CID=0

&A3 &B1 &C1 &D2 &G0 &H1 &I0 &K1
&M4 &N0 &P0 &R2 &S0 &T5 &U0 &Y1

S00=001 S01=000 S02=043 S03=013 S04=010 S05=008 S06=002
S07=060 S08=002 S09=006 S10=014 S11=070 S12=050 S13=000
S15=000 S16=000 S18=000 S19=000 S21=010 S22=017 S23=019
S25=005 S27=000 S28=008 S29=020 S30=000 S31=128 S32=002
S33=000 S34=000 S35=000 S36=014 S38=000 S39=000 S40=001
S41=000 S42=000

LAST DIALED #: T9712310633

OK
ATI11
U.S. Robotics 56K FAX EXT Link Diagnostics...

Modulation V.90
Carrier Freq (Hz) None/1920
Symbol Rate 8000/3200
Trellis Code None/64S-4D
Nonlinear Encoding None/ON
Precoding None/ON
Shaping ON/ON
Preemphasis (-dB) 5/10
Recv/Xmit Level (-dBm) 26/16
Near Echo Loss (dB) 5
Far Echo Loss (dB) 0
Carrier Offset (Hz) NONE
Round Trip Delay (msec) 42
Timing Offset (ppm) 2417
SNR (dB) 46.0
Speed Shifts Up/Down 4/5
Status : uu,5,12N,12.2,-7,0N,0,49.7,15.9
OK
ATI6
U.S. Robotics 56K FAX EXT Link Diagnostics...

Chars sent 2397433 Chars Received 52846317
Chars lost 0
Octets sent 1408747 Octets Received 51902644
Blocks sent 79234 Blocks Received 408326
Blocks resent 31

Retrains Requested 0 Retrains Granted 0
Line Reversals 0 Blers 2894
Link Timeouts 0 Link Naks 11

Data Compression V42BIS 2048/32
Equalization Long
Fallback Enabled
Protocol LAPM/SREJ
Speed 45333/24000
V.90 Peak Speed 48000
Last Call 03:29:22

Disconnect Reason is DTR dropped

OK
ATS$
HELP, S Register Functions (CTRL-S to Stop, CTRL-C to Cancel)

S0 Ring to Answer ON S28 V32 Handshake Time (1/10sec)
S1 Counts # of Rings S29 V.21 answer mode fallback timer
S2 Escape Code Char S30 Reserved
S3 Carriage Return Char S31 Reserved
S4 Line Feed Char S32 Connection bit mapped operations.
S5 Backspace Char 1 = V.8 Call Indicate enable
S6 Wait Time/Dial Tone (sec) 2 = Enable V.8 mode
S7 Wait Time/Carrier (sec) 4 = Reserved
S8 Comma Time (sec) 8 = Disable V.34 modulation
S9 Carrier Detect Time (1/10sec) 16 = Disable V.34+ modulation
S10 Carrier Loss Time (1/10sec) 32 = Disable x2 modulation
S11 Dial Tone Spacing (msec) 64 = Disable V.90 modulation
S12 Escape Code Time (1/50sec) 128 = Reserved
S13 Bit Mapped S33 V.34 & V.34+ Connection setup
1 = Reset ON DTR Loss bit mapped control flags.
2 = Reduced Non-ARQ TX Buffer 1 = Disable 2400 Symbol rate
4 = Set DEL=Backspace 2 = Disable 2743 Symbol rate
8 = Do DS0 ON DTR 4 = Disable 2800 Symbol rate
16 = Do DS0 ON Reset 8 = Disable 3000 Symbol rate
Strike a key when ready . . .
32 = Reserved 16 = Disable 3200 Symbol rate
64 = Disable Quick Retrains 32 = Disable 3429 Symbol rate
128 = Escape Code Hang Up 64 = Reserved
S14 Reserved 128 = Disable Shaping
S15 Bit Mapped S34 V.34 & V.34+ Connection setup
1 = MNP/V.42 Disabled in V.22 bit mapped control flags.
2 = MNP/V.42 Disabled in V.22bis 1 = Disable 8S-2D trellis
encoding
4 = MNP/V.42 Disabled in V.32 2 = Disable 16S-4D trellis
encoding

8 = Disable MNP Handshake 4 = Disable 32S-2D trellis
encoding

16 = Disable MNP Level 4 8 = Disable 64S-4D trellis
encoding

32 = Disable MNP Level 3 16 = Disable Non linear coding
64 = Unusual MNP-Incompatibility 32 = Disable TX level deviation
128 = Disable V.42 64 = Disable Pre-emphasis
136 = Disable V.42 Detect Phase 128 = Disable Pre-coding
S16 Test Modes S35 Reserved
1 = Reserved S36 Reserved
2 = Dial Test S37 Reserved
4 = Reserved S38 Disconnect Wait Time (sec)
8 = Reserved S39 Reserved
Strike a key when ready . . .
16 = Reserved S40 Reserved
32 = Reserved S41 Distinctive Ring options
64 = Reserved 1 = Distinctive Ring Enabled
128 = Reserved 2 = Reserved
S17 Reserved 4 = Reserved
S18 &Tn Test Timeout (sec) 8 = Reserved
S19 Inactivity Timeout (min) 16 = Reserved
S20 Reserved 32 = Reserved
S21 Break Length (1/100sec) 64 = Reserved
S22 Xon Char 128 = Reserved
S23 Xoff Char S42 Reserved
S24 Reserved
S25 DTR Recognition Time (1/100sec)
S26 Reserved
S27 Bit Mapped
1 = V21 Mode
2 = Disable TCM
4 = Disable V32
8 = Disable 2100hz
Strike a key when ready . . .
16 = Enable V23 Fallback
32 = Disable V32bis
64 = Reserved
128 = Software Compatibility Mode

OK

** end copy **

From: Robert Baer on 4 May 2010 23:51

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