On Sat, Dec 3, 2011 at 12:29 PM, Ethan Dicks <ethan.di...@gmail.com> wrote:
(Boosting the signal - look at the date on the original request...) > A friend of mine just returned a modem he got from me decades ago, a > Ventel MD212-plus. It's an early-1980s non-AT-command-set > autodialling modem. The settings are adjusted via a pair of 10-pin > DIP switches accessible from the back. I've checked the web and > bitsavers. So far, all I've found is some old Usenet articles and a > couple of pictures, but no manual or jumper guide. So another friend gave me a Ven-Tel MD212-plus last year. I am still unable to cough up any docs online with the exception of the purpose of switch H1 - it's the pulse-dial/tone-dial switch. The other 19 switches remain mysterious. I have done a bit of circuit tracing of the main connectors (DB25 for EIA comms, DA15 for phone line/possibly diagnostics) and the jumper positions on the mainboard (3 boards inside - top one analog, middle one MCU and support chips and a lot of CMOS, bottom one PSU+NVRAM battery+more analog). Most of the important serial settings are done on the dip switches. The MCU program has an interactive menu system for adding numbers to the onboard NVRAM (appears to be an RCA5101 256x4 CMOS SRAM kept alive with a CR2430 lithium coin cell) and dialing from the NVRAM or interactively. This was a great modem for sticking on a VT100 and interactively dialing into work. It was not a great modem for UUCP because it had a screwy menu system with timings that were expecting a human poking keys not software blasting out commands. Front View: http://d2ydh70d4b5xgv.cloudfront.net/images/2/8/ven-tel-md212-modem-300-1200-baud-bit-sec-2d7bf0f0836905c5e385b6d79336b4af.jpg Rear View: http://d2ydh70d4b5xgv.cloudfront.net/images/7/0/ven-tel-md212-modem-300-1200-baud-bit-sec-f07e2ac87ebe5c016ad9468594fa4e97.jpg Front Panel LEDs: MB | TR | MR | SD | RD | HS | MC | TM Front Panel pushbutton switches: AL | ST | RDL | DL | HS ISTR HS is the 300 baud/1200 baud switch. RDL and DL should be loopback test buttons. AL could be analog loopback. Don't recall off the top of my head what ST might be. There is very little technical detail online about this modem. The vast majority of hits are people asking for a manual or jumper settings. I may have some documentation on an ancient backup tape from the 80s but nothing has surfaced in the past 5 years. Sadly, I have misplaced the one DA15->4p4c phone cable I had. No idea what sort of internal connections/passive components may have been on the DA15 plug but one presumes that the red and green wires from the modular jack went into 2 of the pins on the DA15. Tracing out the entire DA15 revealed some curious stuff, including that very few of the pins were no-connects. If anyone happens to have a cache of 1980s modem docs, perhaps something will surface. Internally, here's what I found after an hour of poking around: F10 - 10-pin DIP switch F1 ? F2 ? F3 ? F4 ? F5 ? F6 ? F7 ? F8 ? F9 ? F10 ? H10 - 10-pin DIP switch H1 Pulse Dial (up) / Tone Dial (down) H2 ? H3 ? H4 ? H5 ? H6 ? H7 ? H8 ? H9 ? H10 ? J1 DB25 1 Protective Gnd (JP5) 2 RxD 3 TxD 4 CTS 5 RTS 6 DSR 7 Signal Gnd 8 DCD 9 Data set testing? 10 Data set testing? 11 NC 12 SDCD (JP1) 13 SRTS (NC) -- 14 STxD (NC) 15 DB/TCLK (sync transmit clk) 16 SRxD (NC) 17 DD/RCLK (sync receive clk) 18 LL (NC) 19 SCTS (NC) 20 DTR 21 RL/SQ (NC) 22 RI 23 CH/CI? 24 DA/ACLK? 25 TM? J2 - DA15 1 NC 2 NC 3 J3 pin 26 4 J3 pin 25 5 to F10 DIP SW ? 6 Gnd 7 J3 pin 20 ? (to be verified) 8 J3 pin 18 ? (to be verified) - 9 J3 pin 5 10 +5 / VCC ? (to be verified) 11 J3 pin 15 Vee / -12V 12 NC 13 NC 14 JP4 pin 3 (open) 15 JP3 pin 3 ? (open) J3 26-pin 0.1" header between digital/MCU board and PSU board [ When I used to use these modems on a daily basis, we never opened them up and fiddled with these jumpers, but I'm including my findings for completeness ] JP1 3-pin with jumper on 1-2 1 B9 pin 6 (1488) 2 J1 pin 12 (DB25 connector) SDCD 3 NC JP2 3-pin with jumper on 1-2 1 1489 @ C9 pin 1 2 DB25 pin ? 3 1489 @ C9 pin 10 JP3 3-pin, no header installed, pin 1-2 jumper on PCB 1 J3 pin 12 2 J3 pin 12 3 J2 pin 15 ? (to be verified) JP4 3-pin, no header installed, pin 1-2 jumper on PCB 1 J3 pin 11 2 J3 pin 11 3 J2 pin 14 (DA15 connector) JP5 2-pin, header and jumper installed 1 GND 2 J1 pin 1 (DB25 connector) JP6 3-pin, no header installed, pin 1-2 jumper on PCB 1 +5V/Vcc 2 ? - via under 8039 MCU @ F/H 4 3 Gnd JP7 3-pin, no header installed, open 1 Gnd 2 P8243 MCS48 I/O expander @ H 7/8 pin 1 (P50) with pullup to Vcc 3 NC JP8 2-pin, no header installed, open 1 ? with pullup to Vcc 2 Gnd JP9 2-pin, no header installed, open 1 ? with pullup to Vcc 2 Gnd JP10 2-pin, no header installed, open 1 ? with pullup to Vcc 2 Gnd
