rpainter@encore.com (Rich Painter) (05/31/90)
I have been experiencing significant problems with the Microcom QX/V.32
modems for many months. These problems come in two basic flavors:
command functions and operational carrier losses.
Operational carrier losses are seen only when the telephone line
exhibits line disturbances. These disturbances are typically pops,
clicks, and stepper chatter which happen intermittently.
Microcom claims that the unit will tolerate these conditions and
continue operating, sometimes in a speed-degraded mode.
Microcom has tested my questionable modems and pronounced them healthy
but the problems still occur.
Below I have summarized my problems. Does ANYONE else have these or
related or other Microcom problems? I have been getting a cold shoulder
from Microcom...
1. Connection interruption (+++) in 9600 and 2400/REL causes improper
response on the serial interface. The usual new line and OK
strings do not appear but junk characters do. This could be a
temporary parity or speed switch. The first command issued
(usually ATH) is executed but junk characters are echoed on the
serial port. The normal command echo sequence is restored
following the first command execution.
2. A problem similar to the previous occurs when the unit is left in
the command mode and set for no answer (S0=0). When the telephone
rings the modem posts a RING string to the serial port. Sometimes
it prints junk characters.
3. When NO CARRIER appears unexpectedly, the REMOTE modem
is permanently hung. It keeps the telephone line off hook, will
not respond to anything sent to the serial port, and will not reset
using the reset button. The unit must be powered off then powered
on to reset it.
4. While connected at 9600 baud, the units will stop passing data.
The test light will flash on then off. The connection will be
maintained forever but no data will be transmitted or received
afterward. Listening in on the telephone line, one hears a
constant-amplitude, constant frequency tone produced by the modem.
The reset button must be pushed to reset this condition and break
the connection. Generally, following this condition the remote
modem is hung as previously described.
5. The LOCAL unit exhibits strange behavior sensitivity to the
numbers stored in the directory. Given a set of eight (8) specific
entries, the unit hangs following issuance of AT\F command. The
modem will reset with the reset button.
6. Remote digital loopback does not work. It reports erroneous
results.
7. The unit will not connect with some modems at 2400 baud and less
without forcing speed to 2400 baud or less (AT%Bx).
+-------------------------------------------------------------------+
| Richard A. Painter |
| Encore Computer Corporation 717-395-{3660,3648} |
| Senior Technical Specialist painter@encore.com |
| RD 1, Box 655A painter@crnlthry.bitnet |
| Warren Center, PA 18851 uunet!gould!painter |
| |
| (formerly Gould Electronics, Computer Systems Division and SEL) |
+-------------------------------------------------------------------+cpcahil@virtech.uucp (Conor P. Cahill) (05/31/90)
In article <126654@infocenter.encore.com> rpainter@encore.com (Rich Painter) writes: > > Below I have summarized my problems. Does ANYONE else have these or > related or other Microcom problems? I have been getting a cold shoulder > from Microcom... I have 3 QXV.32cs and 3 QX3296s and have had some of the same problems. > 1. Connection interruption (+++) in 9600 and 2400/REL causes improper > response on the serial interface. The usual new line and OK I run mine in SX mode so I don't see this problem. > 2. A problem similar to the previous occurs when the unit is left in > the command mode and set for no answer (S0=0). When the telephone > rings the modem posts a RING string to the serial port. Sometimes > it prints junk characters. The junk characters may be comming because the modem has lost track of what bps to run the serial port at. I use SX mode so I can permanently lock the serial port at a given bps. > 3. When NO CARRIER appears unexpectedly, the REMOTE modem > is permanently hung. It keeps the telephone line off hook, will > not respond to anything sent to the serial port, and will not reset > using the reset button. The unit must be powered off then powered > on to reset it. I have seen this on both models. > 4. While connected at 9600 baud, the units will stop passing data. > The test light will flash on then off. The connection will be This is the same kind of stuff as with problem #3. I have it happen all the time on my home phone line and have to use one of my t2500's in PEP mode most of the time. I hate using PEP mode for interactive stuff. V.32 is much better, however v.32 that keeps locking up is unusable when compared to working PEP. I too talked to microcom and they insist that the modems will drop the lines (and carrier and hanup) after a short period of time while I have seen them still on line the monday following a friday lockup. When the lines just have noise these modems work great, but when a certain kind of noise is on the line, they are useless. > 5. The LOCAL unit exhibits strange behavior sensitivity to the > numbers stored in the directory. Given a set of eight (8) specific > entries, the unit hangs following issuance of AT\F command. The > modem will reset with the reset button. I don't use the stored number feature. > 6. Remote digital loopback does not work. It reports erroneous > results. ditto. > 7. The unit will not connect with some modems at 2400 baud and less > without forcing speed to 2400 baud or less (AT%Bx). I have run into several problems with other 2400 baud modems dialing into our modems, but these problems are usually with cheap no-name brands so I haven't spent much time following up with the problem. I have used these modems to do lots of work cross country with great results, it's just some problems with some rather noisy lines that have dissapointed me. -- Conor P. Cahill (703)430-9247 Virtual Technologies, Inc., uunet!virtech!cpcahil 46030 Manekin Plaza, Suite 160 Sterling, VA 22170