From: http://www.apcupsd.com/manual/cables.html

Cables

First, you will need a serial port cable between the APC UPS and your computer running apcupsd. You can use either the cable that came with your UPS (the easiest if we support it) or you can make your own cable. We recommend that you obtain a supported cable directly from APC.

If you already have an APC cable, you can determine what kind it is by examining the flat sides of the two connectors where you will find the cable number embossed into the plastic. It is generally on one side of the male connector.

To make your own cable, first, you must know whether you have a Smart UPS that sends ASCII characters called Smart Signaling, or a "dumb" UPS that uses serial port line voltage signaling, called Simple Signaling.

The "dumb" UPSes are older models such as the BackUPS (not BackUPS Pro) and the ShareUPS Basic Port that use Simple Signaling. Most other UPSes use Smart Signaling. If in doubt consult the Configuration Section of this manual, or the documentation that came with your UPS.

Smart Signaling Cable for SmartUPSes

If you must build your own cable, and you have a Smart UPS, we recommend building the cable as follows:
    SMART-CUSTOM CABLE

 Signal Computer                  UPS
         DB9F                     DB9M
   RxD    2   --------------------  2  TxD  Send
   TxD    3   --------------------  1  RxD  Receive
   GND    5   --------------------  9  Ground

When using this cable with apcupsd specify the following in apcupsd.conf:
  UPSCABLE smart
  UPSTYPE smartups
  DEVICE /dev/ttyS0 (or whatever your serial port is)

Smart Signaling Cable for BackUPS CS Models

If you have a BackUPS CS, you are probably either using it with the USB cable that is supplied or with the 940-0128A supplied by APC, which permits running the UPS in dumb mode. By building your own cable, you can now run the BackUPS CS models (and perhaps also the ES models) using Smart signaling and have all the same information that is available as running it in USB mode.

The jack in the UPS is actually a 10 pin RJ45. However, you can just as easily use a 8 pin RJ45 connector, which is more standard (ethernet TX, and ISDN connector). >Below, you will find a diagram for the CUSTOM-RJ45 cable:

    CUSTOM-RJ45 CABLE

 Signal Computer              UPS     UPS
         DB9F                 RJ45-8  RJ45-10
   RxD    2   ----------------  1      2     TxD  Send
   TxD    3   ----------------  7      8     RxD  Receive
   GND    5   ----------------  6      7     Ground

The RJ45-8 pins are: looking at the end of the connector:

   8 7 6 5 4 3 2 1
 ___________________
 | . . . . . . . . |
 |                 |
 -------------------
         |____|

The RJ45-10  pins are: looking at the end of the connector:

  10 9 8 7 6 5 4 3 2 1
 _______________________
 | . . . . . . . . . . |
 |                     |
 -----------------------
         |____|

When using this cable with apcupsd specify the following in apcupsd.conf:
  UPSCABLE smart
  UPSTYPE smartups
  DEVICE /dev/ttyS0 (or whatever your serial port is)

The information for constructing this cable was discovered and transmitted to us by slither_man. Many thanks!

Simple Signaling Cable for "dumb" UPSes

NOTE. YOU DO NOT HAVE THIS CABLE UNLESS YOU BUILT IT YOURSELF. THE SIMPLE-CUSTOM CABLE IS NOT AN APC PRODUCT.

For "dumb" UPSes using Simple Signaling, if you are going to build your own cable, we recommend to make the cable designed by the Apcupsd team as follows:

         SIMPLE-CUSTOM CABLE
                 
 Signal Computer                  UPS
         DB9F   4.7K ohm          DB9M
   DTR    4   --[####]--*              DTR set to +5V by Apcupsd
                        |
   CTS    8   ----------*---------  5  Low Battery
   GND    5   --------------------  4  Ground
   DCD    1   --------------------  2  On Battery
   RTS    7   --------------------  1  Kill UPS Power

List of components one needs to make the Simple cable:
  1. One (1) male DB9 connector, use solder type connector only.
  2. One (1) female DB9/25F connector, use solder type connector only.
  3. One (1) 4.7K ohm 1/4 watt 5% resistor.
  4. resin core solder.
  5. three (3) to five (5) feet of 22AWG multi-stranded four or more conductor cable.

- Solder the resistor into pin 4 of the female DB9 connector.

- Next bend the resistor so that it connects to pin 8 of the female DB9 connector.

- Pin 8 on the female connector is also wired to pin 5 on the male DB9 connector. Solder both ends.

- Solder the other pins, pin 5 on the female DB9 to pin 4 on the male connector; pin 1 on the female connector to pin 2 on the male connector; and pin 7 on the female connector to pin 1 on the male connector.

- Double check your work.

We use the DTR (pin 4 on the female connector) as our +5 volts power for the circuit. It is used as the Vcc pull-up voltage for testing the outputs on any "UPS by APC" in Simple Signaling mode. This cable may not work on a BackUPS Pro if the default communications are Smart Signaling mode. This cable is also valid for "ShareUPS" BASIC Port mode and is also reported to work on SmartUPSes. However, the Smart Cable described above is much simpler. To have a better idea of what is going on inside apcupsd, for the SIMPLE cable apcupsd reads three signals and sets three:

Reads:
  CD, which apcupsd uses for the On Battery signal when high.
   
  CTS, which apcupsd uses for the Battery Low signal when high.

  RxD (SR), which apcupsd uses for the Line Down 
      signal when high. This signal isn't used for much.

Sets:
  DTR, which apcupsd sets when it detects a power failure (generally
       5 to 10 seconds after the CD signal goes high). It
       clears this signal if the CD signal subsequently goes low
       -- i.e. power is restored.

  TxD (ST), which apcupsd clears when it detects that the CD signal
       has gone low after having gone high - i.e. power is restored.

  RTS, which apcupsd sets for the killpower signal -- to cause the UPS
       to shut off the power.

Please note that these actions apply only to the SIMPLE cable, the signals used on the other cables are different.

Finally, here is another way of looking at the CUSTOM-SIMPLE cable:

APCUPSD  SIMPLE-CUSTOM CABLE

                
Computer Side  |  Description of Cable           |     UPS Side  
DB9f  |  DB25f |                                 |   DB9m  | DB25m
 4    |   20   |  DTR (5vcc)             *below  |    n/c  |
 8    |    5   |  CTS (low battery)      *below  | <-  5   |   7
 2    |    3   |  RxD (no line voltage)  *below  | <-  3   |   2
 5    |    7   |  Ground (Signal)                |     4   |  20
 1    |    8   |  CD (on battery from UPS)       | <-  2   |   3
 7    |    4   |  RTS (kill UPS power)           | ->  1   |   8
n/c   |    1   |  Frame/Case Gnd (optional)      |     9   |  22

Note: the <- and -> indicate the signal direction.


 Optional connections of original SIMPLE-CUSTOM specification
  that are not used.

                4.7K ohm
   DTR    4   --[####]--*              Note needed
                        |
   RxD    2   ----------*---------  3  Not used by Apcupsd

When using this cable with apcupsd specify the following in apcupsd.conf:
  UPSCABLE simple
  UPSTYPE backups
  DEVICE /dev/ttyS0 (or whatever your serial port is)

Other APC Cables that Apcupsd Supports

Apcupsd will also support the following off the shelf cables that are supplied by APC:

940-0020B/C Simple Signal Only, all models.
940-0023A Simple Signal Only, all models.
940-0119A Simple Signal Only, Back-UPS Office, and BackUPS ES.
940-0024[B/C/G] SmartMode Only, SU and BKPro only.
940-0095[A/B/C] PnP (Plug and Play), all models.
940-1524C SmartMode Only
940-0127A/B USB Cables
940-0128A Simple Signal Only, Back-UPS CS in serial mode.

Simple Signaling Features Supported by Apcupsd for Various Cables

The following table shows the features supported by the current version of Apcupsd (3.8.5 or later) for various cables running the UPS in Simple Signaling mode.

Cable Power Loss Low Battery Kill Power Cable Disconnected
940-0020B Yes No Yes No
940-0020C Yes Yes Yes No
940-0023A Yes No No No
940-0119A Yes Yes Yes No
940-0127A Yes Yes Yes No
940-0128A Yes Yes Yes No
940-0095A/B/C Yes Yes Yes No
simple Yes Yes Yes No

Simple UPS Signaling

Apparently, all APC signaling UPSes have the same signals on the output pins of the UPS. The difference at the computer end is due to different cable configurations. Thus, by measuring the connectivity of a cable, one can determine how to program the UPS. This is to be verified.

The signals presented or accepted by the UPS on its DB9 connector using the numbering scheme listed above is:

UPS Pin         Signal meaning
   1     <-     Shutdown when set by computer for 1-5 seconds.
   2     ->     On battery power (this signal is normally low but
                      goes high when the UPS switches to batteries).
   3     ->     Mains down (line fail) See Note 1 below.
   5     ->     Low battery. See Note 1 below.
   6     ->     Inverse of mains down signal. See Note 2 below.
   7     <-     Turn on/off power (only on advanced UPSes only)
   
   Note 1: these two lines are normally open, but close when the
       appropriate signal is triggered. In fact, they are open collector
       outputs which are rated for a maximum of +40VDC and 25 mA. Thus
       the 4.7K ohm resistor used in the Custom Simple cable works 
       quite well.
   
   Note 2: the same as note 1 except that the line is normally closed,
       and opens when the line voltage fails.

The Back-UPS Office 500 signals

The Back-UPS Office UPS has a telephone type jack as output, which looks like the following:
Looking at the end of the connector:

     6 5 4 3 2 1
    _____________
   | . . . . . . |
   |             |
   |  |----------|
   |__|

It appears that the signals work as follows:

    UPS            Signal meaning
 1 (brown)    <-   Shutdown when set by computer for 1-5 seconds.
 2 (black)    ->   On battery power
 3 (blue)     ->   Low battery
 4 (red)           Signal ground 
 5 (yellow)   <-   Begin signaling on other pins
 6 (none)          none

940-0020B Cable Wiring

This diagram is for informational purposes and is not complete. Although we do not know what the black box semi-conductor contains, we believe that we understand its operation (many thanks to Lazar M. Fleysher for working this out).

This cable can only be used on simple signaling UPSes, and provides the On Battery signal as well as kill UPS power. Most recent evidence (Lazar's analysis) indicates that this cable under the right conditions may provide the Low Battery signal. This is to be confirmed.

APC Part# - 940-0020B

 Signal Computer                  UPS
         DB9F                     DB9M
   CTS    8   --------------------  2  On Battery
   DTR    4   --------------------  1  Kill power
   GND    5   ---------------*----  4  Ground
                             |
                  ---        *----  9  Common
   DCD    1  ----|///|-----------   5  Low Battery
                 |\\\|
   RTS    7  ----|///| (probably a
                  ---   semi-conductor)
Thanks to Lazar M. Fleysher for proper

940-0020C Cable Wiring

This diagram is for informational purposes and may not be complete, we don't recommend that use it to build you build one yourself. This cable can only be used on simple signaling UPSes, and provides the On Battery signal, the Low Battery signal as well as kill UPS power. In apcupsd versions 3.8.2 and prior, please set your UPSCABLE to 940-0020B. In version 3.8.3 and later, you may specify the cable as 940-0020C. Please note that this diagram may not be accurate.
APC Part# - 940-0020C

 Signal Computer                  UPS
         DB9F                     DB9M
   CTS    8   --------------------  2  On Battery
   DTR    4   --------------------  1  Kill power
   GND    5   ---------------*----  4  Ground
                             |
                             *----  9  Common
   RTS    7 -----[ 93.5K ohm ]----- 5  Low Battery
                 or semi-conductor

940-0023A Cable Wiring

This diagram is for informational purposes and may not be complete, we don't recommend that use it to build you build one yourself. This cable can only be used on simple signaling UPSes, and apparently only provides the On Battery signal. As a consequence, this cable is pretty much useless, and we recommend that you find a better cable because all APC UPSes support more than just On Battery. Please note that we are not sure the following diagram is correct.
APC Part# - 940-0023A

 Signal Computer                  UPS
         DB9F                     DB9M
   DCD    1   --------------------  2  On Battery
   
                3.3K ohm
   TxD    3   --[####]-*
                       |
   DTR    4   ---------*
   GND    5   ---------------*----  4  Ground
                             |
                             *----  9  Common

940-0095A Cable Wiring

This cable is used with the backupspropnp and the newbackupspro. It is the definitive wiring diagram for the 940-0095A cable submitted by Chris Hanson <cph at zurich.ai.mit.edu>, who disassembled the original cable, destroying it in the process. He then built one from his diagram and it works perfectly.
Construction and operation of the APC #940-0095A cable.
This cable is included with the APC Back-UPS Pro PNP series.


UPS end                                      Computer end
-------                                      ------------
                    47k        47k
BATTERY-LOW (5) >----R1----*----R2----*----< DTR,DSR,CTS (4,6,8)
                           |          |
                           |          |
                           |         /  E
                           |       |/
                           |    B  |
                           *-------|  2N3906 PNP
                                   |
                                   |\
                                     \  C
                                      |
                                      |
                                      *----< DCD (1)     Low Batt
                                      |
                                      |
                                      R 4.7k
                                      3
                                      |
                               4.7k   |
SHUTDOWN (1)    >----------*----R4----*----< TxD (3)            
                           |
                           |  1N4148
                           *----K|---------< RTS (7)      Shutdown

POWER-FAIL (2)  >--------------------------< RxD,RI (2,9) On Batt

GROUND (4,9)    >--------------------------< GND (5)


Operation:

* DTR is "cable power" and must be held at SPACE.  DSR or CTS may be
  used as a loopback input to determine if the cable is plugged in.

* DCD is the "battery low" signal to the computer.  A SPACE on this
  line means the battery is low.  This is signalled by BATTERY-LOW
  being pulled down (it is probably open circuit normally).

  Normally, the transistor is turned off, and DCD is held at the MARK
  voltage by TxD.  When BATTERY-LOW is pulled down, the voltage
  divider R2/R1 biases the transistor so that it is turned on, causing
  DCD to be pulled up to the SPACE voltage.

* TxD must be held at MARK; this is the default state when no data is
  being transmitted.  This sets the default bias for both DCD and
  SHUTDOWN.  If this line is an open circuit, then when BATTERY-LOW is
  signalled, SHUTDOWN will be automatically signalled; this would be
  true if the cable were plugged in to the UPS and not the computer,
  or if the computer were turned off.

* RTS is the "shutdown" signal from the computer.  A SPACE on this
  line tells the UPS to shut down.

* RxD and RI are both the "power-fail" signals to the computer.  A
  MARK on this line means the power has failed.

* SPACE is a positive voltage, typically +12V.  MARK is a negative
  voltage, typically -12V.  Linux appears to translate SPACE to a 1
  and MARK to a 0.

940-0095B Cable Wiring

This diagram is for informational purposes and may not be complete, we don't recommend that use it to build you build one yourself.
APC Part# - 940-0095B

 Signal Computer                  UPS
         DB9F                     DB9M
   DTR    4   ----*
   CTS    8   ----|
   DSR    6   ----|
   DCD    1   ----*
   GND    5   ---------------*----  4  Ground
                             |
                             *----  9  Common
   RI     9   ----*
                  |
   RxD    2   ----*---------------  2  On Battery
   TxD    3   ----------[####]----  1  Kill UPS Power
                        4.7K ohm

940-0119A Cable Wiring

This diagram is for informational purposes and may not be complete, we don't recommend that use it to build you build one yourself. This cable is used with the BackUPS Office UPSes.
APC Part# - 940-0119A

    UPS      Computer
    pins     pins      Signal             Signal meaning
 1 (brown)    4,6      DSR DTR     <-   Shutdown when set by computer for 1-5 seconds.
 2 (black)    8,9      RI  CTS     ->   On battery power
 3 (blue)     1,2      CD  RxD     ->   Low battery 
 4 (red)       5       Ground
 5 (yellow)    7       RTS         <-   Begin signaling on other pins 
 6 (none)     none

BackOffice ES

The BackUPS ES has a straight through serial cable with no identification on the plugs. To make it work with apcupsd, specify the UPSCABLE 940-0119A and UPSTYPE backups. The equivalent of cable 940-0119A is done on a PCB inside the unit. Thanks to William Stock for supplying us with the information about the straight through cable, the PCB, and the following diagram:

computer           ----------- BackUPS-ES -----------------
 DB9-M              DB-9F
  pin    signal      pin

   4      DSR   ->    4 --+
                          |  diode   resistor
   6      DTR   ->    6 --+---->|----/\/\/\---o kill power

   1      DCD   <-    1 --+
                          |
   2      RxD   <-    2 --+----------------+--o low battery
                                           |
   7      RTS   ->    7 --------+--/\/\/\--+
                                |
                                +--/\/\/\--+
                                           |
   8      RI    <-    8 --+----------------+--o on battery
                          |
   9      CTS   <-    9 --+

   5      GND   ---   5 ----------------------o ground

   3      TxD         3 nc

BackUPS ES and CS in Serial mode with Cable 940-0128A

Though these UPSes are USB UPSes, APC supplies a serial cable (typically with a green DB9 F connector) that has 940-0128A stamped into one side of the plastic serial port connector. The other end of the cable is a 10 pin RJ45 connector that plugs into the UPS (thanks to Dean Waldow for sending me a cable!). Apcupsd version 3.8.5 and later supports this cable when specified as UPSCABLE 940-0128A and UPSTYPE backups. However, running in this mode much of the information that would be available in USB mode is lost. In addition, when apcupsd attempts to instruct the UPS to kill the power, it begins cycling about 4 times a second between battery and line. The solution to the problem (thanks to Tom Suzda) is to unplug the UPS and while it is still chattering, press the power button (on the front of the unit) until the unit beeps and the chattering stops. After that the UPS should behave normally and power down 1-2 minutes after requested to do so.

An amazing discovery by slither_man allows one to build a CUSTOM-RJ45 cable (documented above) and run the BackUPS CS (and probably also the ES) in Smart mode. Running it this way provides all the same information that you would get by running it in USB mode. As a consequence, we recommend that you either purchase (where I don't know) or build your own CUSTOM-RJ45 cable rather than use the 940-0128A cable.

Thanks to all the people who have helped test this and have provided information on the cable wiring, our best guess for the cable schematic is the following:


computer        --------- Inside the Connector---------  UPS
 DB9-F          |                                     |  RJ45
  pin - signal  |                                     |  Pin - Color
                |                                     |
   4     DSR  ->|---+                                 |
                |   |  diode   resistor               |
   6     DTR  ->|---+---->|----/\/\/\---o kill power  |  8  Orange
                |                                     |
   1     DCD  <-|----+                                |
                |    |                                |
   2     RxD  <-|----+----------------+--o low battery|  3  Brown
                |                     |               |
   7     RTS  ->|----------+--/\/\/\--+               |
                |          |                          |   
                |          +--/\/\/\--+               |
                |                     |               |
   8     RI   <-|----+----------------+--o on battery |  2  Black
                |    |                                |
   9     CTS  <-|----+                                |
                |                         signal      |
   5     GND  --|-----------------------o ground      |  7  Red
                |                                     |
   3     TxD    |                                     |
                |                         chassis     |
   Chassis/GND  |-----------------------o ground      |  4  Black
                |                                     |
                |          Not connected              |  1, 5, 6, 9, 10
                -------------------------------------- 

The RJ45 pins are: looking at the end of the connector:

  10 9 8 7 6 5 4 3 2 1
 _______________________
 | . . . . . . . . . . |
 |                     |
 -----------------------
         |____|

Win32 Implementation Restrictions for Simple UPSes

Due to inadequacies in the Win32 API, it is not possible to set/clear/get all the serial port line signals. apcupsd can detect: CTS, DSR, RNG, and CD. It can set and clear: RTS and DTR.

This imposes a few minor restrictions on the functionality of some of the cables. In particular, LineDown on the Custom Simple cable, and Low Battery on the 0023A cable are not implemented.

Internal Apcupsd Actions for Simple Cables

This section describes how apcupsd 3.8.5 (March 2002)
treats the serial port line signals for simple cables.

apcaction.c: 
   condition = power failure detected
   cable = CUSTOM_SIMPLE
   action = ioctl(TIOCMBIS, DTR)      set DTR (enable power bit?)

apcaction.c: 
   condition = power back
   cable = CUSTOM_SIMPLE
   action = ioctl(TIOCMBIC, DTR)      clear DTR (clear power bit)
   action = ioctl(TIOCMBIC, ST)       clear ST (TxD)

apcserial.c: 
   condition = serial port initialization
   cable = 0095A, 0095B, 0095C
   action = ioctl(TIOMBIC, RTS)       clear RTS (set PnP mode)

   cable = 0119A, 0127A, 0128A
   action = ioctl(TIOMBIC, DTR)       clear DTR (killpower)
   action = ioctl(TIOMBIS, RTS)       set   RTS (ready to receive)

apcserial.c: 
   condition = save_dumb_status
   cable = CUSTOM_SIMPLE
   action = ioctl(TIOMBIC, DTR)       clear DTR (power bit?)
   action = ioctl(TIOMBIC, RTS)       clear RTS (killpower)

   cable = 0020B, 0020C, 0119A, 0127A, 0128A
   action = ioctl(TIOMBIC, DTR)       clear DTR (killpower)

   cable = 0095A, 0095B, 0095C
   action = ioctl(TIOMBIC, RTS)       clear RTS (killpower)
   action = ioctl(TIOMBIC, CD)        clear DCD (low batt)
   action = ioctl(TIOMBIC, RTS)       clear RTS (killpower) a second time!

apcserial.c:
   condition = check_serial

   cable = CUSTOM_SIMPLE
   action = OnBatt = CD
   action = BattLow = CTS
   action = LineDown = SR

   cable = 0020B, 0020C, 0119A, 0127A, 0128A
   action = OnBatt = CTS
   action = BattLow = CD
   action = LineDown = 0

   cable = 0023A
   action = Onbatt = CD
   action = BattLow = SR
   action = LineDown = 0

   cable = 0095A, 0095B, 0095C
   action = OnBatt = RNG
   action = BattLow = CD
   action = LineDown = 0


apcserial.c
   condition = killpower

   cable = CUSTOM_SIMPLE, 0095A, 0095B, 0095C
   action = ioctl(TIOMCBIS, RTS)      set RTS (kills power)
   action = ioctl(TIOMCBIS, ST)       set TxD       

   cable = 0020B, 020C, 0119A, 0127A, 0128A
   action = ioctl(TIOMCBIS, DTR)      set DTR (kills power)

RS232 Wiring and Signal Conventions

DB-25
Pin #
DB-9
Pin #
Name DTE-DCE Description
1 -- FG --- Frame Ground/Chassis GND
2 3 TD ---> Transmitted Data, TxD
3 2 RD <--- Received Data, RxD
4 7 RTS ---> Request To Send
5 8 CTS <--- Clear To Send
6 6 DSR <--- Data Set Ready
7 5 SG ---- Signal Ground, GND
8 1 DCD <--- Data Carrier Detect
9 -- -- --- Positive DC test voltage
10 -- -- --- Negative DC test voltage
11 -- QM <--- Equalizer mode
12 -- SDCD <--- Secondary Data Carrier Detect
13 -- SCTS <--- Secondary Clear To Send
14 -- STD ---> Secondary Transmitted Data
15 -- TC <--- Transmitter (signal) Clock
16 -- SRD <--- Secondary Receiver Clock
17 -- RC ---> Receiver (signal) Clock
18 -- DCR <--- Divided Clock Receiver
19 -- SRTS ---> Secondary Request To Send
20 4 DTR ---> Data Terminal Ready
21 -- SQ <--- Signal Quality Detect
22 9 RI <--- Ring Indicator
23 -- -- ---> Data rate selector
24 -- -- <--- Data rate selector
25 -- TC <--- Transmitted Clock

Pin Assignment for the Serial Port (RS-232C), 25-pin and 9-pin, Female End

     13                         1         5         1
   _______________________________      _______________
   \  . . . . . . . . . . . . .  /      \  . . . . .  /    RS232-connectors
    \  . . . . . . . . . . . .  /        \  . . . .  /     looking into the
     ---------------------------          -----------      end of the cable.
     25                      14            9       6

 The diagram above represents the Female end of the cable. The
 male end is the same, but looking from inside the cable.
          
   DTE : Data Terminal Equipment (i.e. computer)
   DCE : Data Communications Equipment (i.e. UPS)
   RxD : Data received; 1 is transmitted "low", 0 as "high"
   TxD : Data sent; 1 is transmitted "low", 0 as "high"
   DTR : DTE announces that it is powered up and ready to communicate
   DSR : DCE announces that it is ready to communicate; low=modem hang-up
   RTS : DTE asks DCE for permission to send data
   CTS : DCE agrees on RTS
   RI  : DCE signals the DTE that an establishment of a connection is attempted
   DCD : DCE announces that a connection is established

Ioctl to RS232 Correspondence

#define TIOCM_LE        0x001
#define TIOCM_DTR       0x002
#define TIOCM_RTS       0x004
#define TIOCM_ST        0x008
#define TIOCM_SR        0x010
#define TIOCM_CTS       0x020
#define TIOCM_CAR       0x040
#define TIOCM_RNG       0x080
#define TIOCM_DSR       0x100
#define TIOCM_CD        TIOCM_CAR
#define TIOCM_RI        TIOCM_RNG
#define TIOCM_OUT1      0x2000
#define TIOCM_OUT2      0x4000