idallen@watmath.UUCP (10/30/85)
Product description and evaluation:
Fujitsu America Modem M1935D (FCC #B258QM-13989-DM-E) Ser. #3394
Bell 212-A CCITT V.24/V.28 CCITT V.22bis compatible (1200/2400 bps)
Synchronous or Asynchronous
Ringer Equivalence: 0.6B
Warranty: One year.
LED Status Lights:
DTR "Data Terminal Ready" asserted by DTE (pin 20)
DSR asserted by modem (pin 6)
CI ring detected by modem (pin 22)
RTS "Request To Send" asserted by DTE (pin 4)
CTS "Clear To Send" asserted by modem (pin 5)
CD "Carrier Detect" asserted by modem (pin 8)
TD transmitted data (pin 2)
RD received data (pin 3)
HS high speed 2400 bps indicator (pin 12)
ERR errors in modem self-test patterns
TST modem is in self-test mode (pin 25)
DTE Interface Lead Status Indications:
pin 5 - Clear to Send
pin 6 - Data set Ready
pin 8 - Carrier Detect
pin 12 - select data speed output
pin 22 - calling indicator
pin 25 - test indicator
Panel buttons:
Talk/Data - switch in/out phone jack
Originate/Answer - reverse originate/answer tone frequencies
Low-Speed/High-Speed - lock modem to 1200 bps
Digital Loopback test
Analog Loopback test
Remote Diagnostic test
Rear DIP Switches:
Synchronous Data Transmit Clock Source (internal, external, looped)
Asynchronous Character Bit Length (8,9,10,11 bits)
1200 bps modulation (CCITT V.22, Bell 212A)
Synchronous or Asynchronous DTE
Pulse or DTMF dialling
Internal Switches:
Enable RDL via pin 21
Enable modem speed control via pin 23
Enable AL via pin 18
Enable DTR via pin 20
Enable incoming Remode Digital Loopback commands
Carrier Detect Level (-33dBm, -43dBm)
Hold 1200 bps carrier in either V.22 or 212 mode
Enable RTS via pin 4
On-hook/off-hook switch (for leased lines)
Option straps on PCB:
Speaker volume (off,low,high)
Oscilloscope test points
Initial Performance:
No errors noted at 1200 bps between my home Hayes 1200 and the
Fujitsu operating at 1200 bps, during 8 hours of log-on time.
Commands:
Dial a number. That's all. No second-dial-tone detect; 2-second
pauses are available. Tone and pulse dial are possible in the same
number.
UUCP:
The modem doesn't talk back at all, ever. It doesn't confirm numbers
or echo characters. What little information it tells you it tells you
via signals on the RS-232 plug. UNIX doesn't provide an easy means to
test or manipulate the RS-232 signals; this means UUCICO can't tell when
the modem is alive, or when it successfully goes on-line. You just send
the telephone number into a black hole and hope it works.
The modem doesn't auto-baud to the characters typed at it. To dial
out at 1200 bps you have to send a signal on pin 23 of the RS-232
plug to hold the modem in low-speed mode, or push the button on the
front of the modem. Neither of these options is easy to do with your
stock UUCICO.
Where the USR Courier (tested previously) failed miserably, this modem
works fine. We got 210 bytes/sec at 2400 bps via our SL-1 and Foreign
Exchange to UTZOO in Toronto. The Courier managed 24 (twenty-four)
bytes/sec over the same line. A call to LINUS in Boston also gave us
the full 210 bytes/sec. Looks like the folks at USR need to re-examine
their 2400 bps transmission; this Fujitsu works very well.
Summary:
If only this modem would optionally be more chatty, so UUCICO could
tell what state it was in. Using the proper EIA and CCITT RS-232
signals is admirable, but UNIX can't set them and doesn't know what to
do with them. We can't dedicate a line to 2400 bps; we need a modem
that can be told (in ASCII) to change data rates between 1200 and 2400
bps. This modem can't do that.
If you've got hardware that can read and set the RS-232 pins, this
looks like a quality modem. I'm not crazy about the arbitrary choice
of which switches Fujitsu placed inside the box and which are on the back
panel, but most of them are "set-once-and-forget" anyway. I'm
pleased that this modem succeeded where the USR Courier failed. Now, I
just have to find a modem that is as chatty as the USR Courier but as
technically good as this Fujitsu.
--
-IAN! (Ian! D. Allen) University of Waterloo