FAXCON - the voice & fax memory
Operating instruction - firmware status 2.20
©1994-99 Michael Klingel

Please note:

The translation of my site is still in progress. Some pages might have errors in translation on it, others might be available only in german language. If links have no function, please look at the
german pages instead.

General information

line-up * operation * status fax * test * configuration

power failure / battery * class 2 and class 2.0 * class 1 * meaning of the fax adjustments * meaning of the modem initialization string * date and time

Further functions
fax switch functions * manually taking over a fax call * uu-dump of the stored fax pages * automatic forwarding of faxes * optional status indicator and switching outputs


General information

With FAXCON the owner of a modern modem is able to be constantly attainable by fax. Since FAXCON is conceived as a buffer, the benefits of fax processing with a computer are not lost, although the computer is not directly involved in reception. The stored faxes can be forwarded to the normally used fax software at any time. FAXCON thereby behaves fully transparent. The transfer runs in such a way, as if a fax would be directly received.

FAXCON has a low power consumption and can be equipped with 128 or 512 KByte of memory. Depending on the layout of the received faxes, about 4 or 16 fax pages can be stored.

Characteristics of FAXCON:

Conditions for the operation of the device:

For the modem FAXCON behaves like a computer with fax software and in reverse. For actual fax reception and decoding thus further the fax software on the computer is responsible.

It is not meant as a replacement for a conventional telefax device in large companies. Rather it is meant for private users or small firms, who only receive a limited number of faxes and already own a suitable modem.

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FAXCON must first be installed into the consisting serial connection between modem and computer. Therefore there are two 25-pin D-SUB-connectors on the back. The modem is connected to the male connector, the computer to the female one. For that purpose an additional cable is required. The plug power pack (approx. 7V AC od. 9V DC) has to be connected to the current supply socket. After these preparations FAXCON can be switched on with the power switch.


The operation is done with two push-buttons, while two light emitting diodes (led) display the operating condition. Additionally FAXCON can be removed completely from the signal path of the serial connection between modem and computer with the rotary selector in position "standby" (down). This is required for the normal operation of the modem (data-communications, directly receive fax, send fax). For fax reception and forwarding stored faxes the rotary selector must be in position "operation" (up).

Directly after power-up the memory is checked (both leds are on). In the event of an error the leds flash alternating after the test. If one or both push-buttons are pressed on power-up, additionally further functions are executed (see overview).

Subsequently, the green led is on, the red led is off. FAXCON is now in initial mode. If the red push-button is pressed briefly, the red led displays that FAXCON is connected with the modem. If this is switched on, it is initialized and FAXCON waits for incoming fax callings, which become automatically received and buffered. During reception the green led flashes rapidly, or even constantly lights up.

The receive mode can be terminated by a long operation of the red push-button. The red led turns off and the green led is on. FAXCON is now in initial mode again.

A long pressure on the green push-button switches into the operating mode for forwarding received faxes to the fax software on the computer. The green led flashes fast and the red is off. FAXCON is now connected with the computer and the reception can be started in the fax software. The fax pages are transferred from the buffer to the computer and received there. When all faxes are transferred, FAXCON automatically switches into the initial mode again.

As soon as at least one fax was received and stored, this is signaled by repeated short flashing signals of the green led in the initial mode and in the receive mode. The number of flashing signals (up to 8) thereby reflects the stored fax pages.

Received faxes can be deleted after they were forwarded at least once. To do so the red push-button must be pressed long in the initial mode. This deletes all stored fax pages, the individual deletion of fax pages is not possible. (Note: Individual deletion of fax pages is possible since firmware v2.29)

Status fax

After forwarding the stored fax pages, an additional status fax can be output, which contains all important information of the stored pages. This function is activated at default.

In particular the actual reception point in time with date and time is output here. Beside that the FAX identification of the transmitting station, the session parameters as well as the page status (interesting with multi-page faxes) is indicated.

The setting is done by bit 6 of the type 1 parameter.


In order to test the forwarding of a fax, without having actually received one, as well as to check the configuration, a test fax can be build. To do so, the red push-button is to be pressed on power-up.

If the push-button is pressed longer than 5 seconds, additionally a two-page test fax is created.

Since the test fax is created on power-up, the contained information refers to this point in time. Later modifications of the configuration are only considered in the test fax after the next power-up.



Fax identification and fax adjustments can be configured automatically according to the settings made in the used fax software. To enable this, the green push-button is to be pressed during power-up of FAXCON. Again a test fax is created. When forwarding to the computer the configuration is modified according to the ssettings transmitted by the fax software.

The other adjustments must be changed manually if necessary. In many cases however no further configuration is necessary.


The configuration mode is entered as follows: Push and hold green push-button -> press red push-button briefly -> release green push-button. The two leds turn off. On the computer a terminal program can be started. With the aid of this, the command ATFAXCON must be transmitted. Thereby all usual baud rates are permitted: 2400...115200 bit/seconds (in each case 8N1; 8 data bits, no parity, 1 stop bit). The configuration menu of FAXCON appears subsequently.

                FaxCon v2.20 - 128KByte
              (c) 1994-98 Michael Klingel

   (A) FAX identification: "     +49 1111 222222" 
   (B) FAX adjustments:    1,5,0,2,0,0,0,0 
   (C) modem init:         &FE0M0L0V1&D0S0=0H 
   (D) number of rings:    1 
   (E) byte delay:         99 
   (F) baud rate modem:    19200 
   (G) date and time:      Mo,00.00. 00:00 
   (W) further adjustments 
   (X) end (without save)
   (S) save configuration

   receive: class 2 - forward: class 2

The heading contains the size of the identified memory as well as the version specification of the firmware. The footing line shows the used Classes (2, 2.0 or 1).

The menu options are selected by input of the letter placed in front. If so far still no modifications were made, the defaults from the ROM are displayed.

Under fax identification the own fax number can be input. Only the digits "0"..."9" as well as the character "+" and a space should be used.

The initialization string modem init and the fax adjustments should be changed only if the effect is clear to you and the modification is actually required.

If necessary the number of rings before going off hook and a delay between the bytes transferred to the computer can be adjusted (byte delay). This delay guaranties that also in interaction with slower computers no data is lost during the serial transfer. With fast computers, in particular with buffered serial interface (FIFO), the value can normally be set to 1.

Under baud rate modem the baud rate, which FAXCON used to access the modem can be adjusted. Usually this is done with 19200 bit/seconds.

The selection date and time finally permits changes to the clock.

The menu option further adjustments leads to a submenu with extended adjustment possibilities.

   *** further adjustments ***

   --- general 
   (A) special flags:      00001000b 
   (B) memory reserve:     0 
   (C) modem FAX init:  
   (D) modem answerstring: A
   --- fax-switch type 1 
   (E) type 1 parameter:   01011001b 
   (F) spec. answerstring: A
   --- fax-switch type 2 
   (G) dial string 1:      H 
   (H) DLE string 1:    
   (I) dial string 2:      H 
   (J) DLE string 2:       ef 
   (K) fax detect time:    40 
   (L) calling tone freq.: 0 
   (M) answering set...
   (X) back to the main menue

   receive: class 2 - forward: class 2

Under memory reserve a minimum size for free memory can be configured. In case memory gets below, the receive mode will be left. The size of the free memory is counted in 32 KByte blocks (1...16). The standard entry 0 means the receive mode is left with fewer than 8 KByte free memory. When the memory limit is reached while receiving a fax, this is stored completely or till the memory is full, independently of the adjustment.

The initialization string modem FAX init is uesd to transmit additional statements to the modem if necessary, after this was set before into the fax mode.

The modem answerstring (default "A") can be modified, if the modem requires another statement for call acceptance.

The further menu options are required for the fax switch functions.

The special flags serves for the selection of different functions. Each flag can be set and reset individually. A set flag activates the indicated function. After calling this menu option a further submenu appears.

   special flags ('-' not set, 'x' set):

   - (0) Class 2.0 when receiving
   - (1) Class 2.0 when forwarding
   - (2) bit order when forwarding
   x (3) automatic selection Class 2/2.0
   - (4) fax-switch-function
   - (5) fax-switch-function type 2
   - (6) voicemodem when forwarding
   - (7) forward when memory full

   (flag number) set/reset, (X) back

The flags are set or reset by input of the flag number. By default only the flag automatic selection Class 2/2.0 is set, which means FAXCON automatically selects the required Class. The flags are described in this guidance in the paragraphs concerned (Class 2 and Class 2.0, fax switch function, automatic forwarding of faxes).

Leaving the configuration routine:

The submenus can be left in each case with "X". The complete configuration routine is terminated with "S" or "X", depending on whether new adjustments are to be stored or not.

Default values:

In order to reset the configuration of FAXCON, the factory-set default values can be loaded. To do so, both push-buttons are to be kept pressed when switching on FAXCON.

This is possibly necessary with a change of the firmware version.

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Power failure / battery

With a power failure the built in battery takes over the supply of FAXCON. To identify this status, the leds light up more darkly than normal in this case. The function of FAXCON is ensured also in this case. Presupposed the connected modem is ready for use, it is possible to receive a fax even during a power failure. In each case the modem is again initialized after the power failure.

With only rarely occurring power failures the life of the battery is essentially limited by its durability. To prevent the battery from defects it should be replaced about every two years.

In order not to shorten the life of the battery unnecessarily, it should be paid attention to the fact that with switched on device the power-plug is plugged in and the leds light up brightly.

Class 2 and Class 2.0

FAXCON can be used with Class 2 and Class 2.0 modems and software. The selection takes place automatically, if with the special flags automatic selection Class 2/2.0 is activated. This is the standard adjustment.

If the modem and/or the fax software supports both Classes, Class 2 is preferred. In addition, with the setting Class 2.0 when receiving and Class 2.0 when forwarding Class 2.0 can an be preferred.

The two latter special flags additionally are used for the Class setting, if the automatic selection is not activated. In each case the used Class is displayed in the configuration menu.

Also possible is a "mixed-mode" operation, thus receiving with a Class 2.0 modem and forwarding to a Class 2 software or the other way around. The bit order of the fax page is adapted automatically thereby so that with the usual modems and fax programs the fax should be directly readable.

If that is not the case, the bit order can be turned around with the special flag bit order when forwarding.

Special abilities of Class 2.0 should not be used in connection with FAXCON. This normally corresponds to the standard adjustment of the modems.

Class 1

Some voice software allow the use of fax modems only with Class 1. Therefore FAXCON can also behave like such a modem when forwarding.

The functional capacity here depends very much on the used software and cannot be guaranteed. Thus the use of a "normal" fax software with Class 2/2.0 is recommended.

If the automatic selection Class 2/2.0 is activated in the special flags, also Class 1 is accepted.

Thus also receiving faxes with Class 1 modems is possible.

Meaning of the fax adjustments

The fax adjustments describe the abilities of a fax modem. The eight parameters VR,BR,WD,LN,DF,EC,BF,ST are separated by commas and have the following meaning:

VR vertical resolution 0 normal
1 fine
BR bit rate 0 2400 bit/s
1 4800 bit/s
2 7200 bit/s
3 9600 bit/s
4 12000 bit/s
5 14400 bit/s
WD side width 0 1728pels on 215mm
1 2048pels on 255mm
2 2432pels on 303mm
LN side length 0 A4, 297mm
1 B4, 364mm
2 unlimited
DF coding 0 1-D Huffman
1 2-D READ
EC error correction 0 none
BF binary file transfer 0 none
ST scantime per line only interesting for fax devices
(pels = picture elements = pixels)

If the fax adjustments in the configuration of FAXCON are modified manually, it is to be made certain that the used fax software also supports the settings.

The parameters EC and BF should have the value 0, ST is without meaning for the function of FAXCON and can also be set to 0.

Meaning of the modem initialization string

In the configuration mode of FAXCON the initialization string for the modem can be set with modem init. This ensures for the fact that the modem is in a status suitable for FAXCON. Normally no modifications should be required. If nevertheless, the individual commands and their meaning are listed here. If necessary the initialization string can be adapted in such a way using the own modem manual.

command meaning
&F load standard configuration
E0 switch off command echo
M1 loudspeaker on during dial-up
L1 loudspeaker on low volume
V1 modem responses in plain text
&D0 ignore DTR changes
S0=0 automatic answer off
H interrupt connection, go on hook

The loudspeaker adjustments concerned can be changed as desired. Thus with the command "M0" instead of "M1" the loudspeaker will always be turned off.

Date and time

FaxCon consideres two sources for date and time:

The firmware implements an internal clock (hour/minutes) with 7-day-calender (Mo...Su). After power-up of FaxCon this clock starts with Mo, 00:00.

For an exact time-of-day, which continues running also after switching off, an optional clock module can be connected at the I2C-bus. Then additionally a 4-year-calender with date (day, month, leap year info) is available.

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Further functions

Fax switch functions

FAXCON supports two different fax switch functions.

Type 1 - Modem and telephone/answering set connected to one line:

Telephone/answering set are connected behind the modem. An incomming call is picked up as usual with telephone/answering set.

An optional additional circuit checks whether a fax tone is received at the beginning of a call. Only in this case the modem goes on line and FAXCON receives the fax. If no fax tone is identified, FAXCON behaves passively and the voicecall can be continued like usual.

Condition for this operating mode is that the used modem is able to take over the line from telephone/answering set.

If no other device pickes up the incoming call, FAXCON nevertheless goes on line after receiving the number of rings configured. If this is not required, the value 0 must be set.

This type of fax switch is activated by the special flag fax switch function, the flag fax switch function type 2 must not be set.

To take over the line FAXCON transmits the command "A" to the modem according to standard. If necessary the string can be modified under spec. answerstring, which is configured in the submenu "further adjustments".

Additionally the criteria for the fax tone identification can be set under type 1 parameter:

Meaning of the bits:

Bit 7 6 5 4 3 2 1 0
Meaningstatus indicatorstatus faxtolerance (%) period (seconds) calling tones (number)
0: off 0: off 00: 15 00: 5 00: 1
1: on 1: on 01: 25* 01: 8 01: 2*
10: 35 10: 13* 10: 3
11: 50 11: 18 11: 4
"*" = default
standardized fax tone: 1100 Hertz, 0.5sec tone, 3sec pause, +/-15%

Type 2 - Modem and telephone/answering set at a telephone system:

Here modem and telephone/answering set are each connected to a seperate connector of the telephone system. The modem receives an incoming call and interconnects the call to telephnone/answering set, if within a given time no fax is identified. Otherwise the fax is received.

The adjustments are made in the configuration mode in the submenu "further adjustments". The waiting period is adjustable under fax detect time (1/10 seconds). To prevent the caller from disconnection, before and after the period a tone can be generated. In addition with call audio frequency the desired frequency is set (10Hz resolution). Values 30...255 for 300...2550 Hertz are permitted, with 0 meaning, that no tone is played.

A short press on the red push-button forces FAXCON to receive a fax, even if no fax tone is identified by the modem.

Condition for this operating mode is a voice-capable modem, which outputs the sequence <DLE>"c" with an identified fax tone.

This type of fax switch is activated by the special flags fax switch function and fax switch function type 2.

The string, which is transmitted to the modem for interconnecting, can be adjusted under dial string 1. A possible string could look like this:

X3 modem ignores dial tone
S8=3 pause 3 seconds with comma
DT tone dial
! flash
21 internal number of telephone/answering-set
, pause (see S8)
; command mode
H go on hook

Default is "H", i.e. the modem goes on hook, if no fax was identified.

Additionally FAXCON can interconnect to a further internal line, dependent on the tones identified on the line. The string necessary for it is entered under dial string 2.

The selection, with which tone which string is transmitted to the modem, is made by the two adjustments DLE string 1 and DLE string 2. Here in each case up to three tones can be entered. Selectable are (if necessary look up in the modem manual):

DTMF tones: "0"..."9", "A"..."F", "*", "#"
Modem tones: call tone "e", answering tone "f"
FAXCON:joker for all digits "?"


   Dial string 1:      ..string for calling "normal" telephone..
   DLE string 1:       ?
   Dial string 2:      ..string for calling "secret" telephone..
   DLE string 2:       *# 
   fax detect time:    45
FAXCON goes on line and analyses the tones on the line for a period of 4.5 seconds ("45"). If during this time a DTMF digit is identified ("?"), the calling immediately goes to the "normal" telephone. If a DTMF-* or -# is identified ("*#"), the calling immediately goes to the "secret" telephone.

If no tone is identified, the calling goes to the "normal" telephone after the configured detection time. Of course also further the fax is received with identified fax tone.

Note: If one of the tones specified under DLE string 2 is identified, FAXCON additionally signals this by a 80 milliseconds long pulse at bit 4 of port expander 2 .

The answering set still is in the development. The features can be found in the supplement.

Manually taking over of a fax call

If a fax is to be received during a consisting voice call, the red push-button must briefly be pressed only. The modem afterwards goes on line and receives the fax. To enable this the fax switch function type 1 must be activated. Its conditions apply here also (the additional circuit for fax tone identification is naturally not necessary).

UU dump of the stored fax pages

If necessary the stored fax pages can also be transferred with the help of a terminal program (thus without fax software) by FAXCON to the computer. To do so, in submenu "further adjustments" in the configuration mode the key "+" must be pressed. In the following the pages are output uu-encoded. After decoding with a uu-decoder the pages can be viewed with every fax viewer capable of displaying raw fax pages.

Automatic forwarding of faxes

This operating mode is activated by the special flag forward with full memory and ensures for the fact that with full memory the faxes stored so far are forwarded to the fax software on the computer.

In addition the computer can be switched on with one of the switching outputs. Subsequently, FAXCON waits a maximum of 10 minutes for a reaction of the fax software and transfers the faxes. If no error occurs, the memory is cleared thereafter.

2 minutes after the final statement of the fax software the computer is switched off with the switching output. With the aid of the statement "ATS1=x" (x=5...255, in seconds) also an absolute time to power-off can be set. FAXCON acknowledges this statement with "OK", waits the desired time interval without further reactions an statements and then switches the computer off. Subsequently, FAXCON again goes on reception and waits for incoming faxes.

The slow flashing green LED of FAXCON displays that faxes were automatically forwarded, but no faxes were buffered further. This display is reset, if receive-, forward- or configuration mode is activated manually.

Condition for switching the computer is the optional port expander for the switching outputs and a suitable wiring.

The automatic switching on of the PC also functions with the test fax. To enable this, under memory reserve 4 (128K memory) or 16 (512K memory) has to be entered.

Optional status indicator and switching outputs

The firmware can use two 8-bit port-expanders (PCF8574), which are connected at the I2C-bus.

Port-expander 1 - Status indicator:

Here a 7-segment-led-display can be connected for the output of the respective operating condition (additional to the two leds according to standard). The meanings of the output characters are:

In receive (R) or forward mode (F)
display offwaiting for incoming call (R)
Iinitializing of modem (R,F)
Lringing (R,F)
ooff hook (R)
Hhangup - go on hook (R,F)
A...Efax phases A...E (R,F)
After power-up
1check push-buttons
2memory test
2.memory error occured
3loading of default configuration
4creating testfax
Other ones
Yconfiguration mode

In the receive mode alternatively the number of stored fax pages can be displayed when waiting for a calling.

The adjustment is made by bit 7 of the type 1 parameter.

Port-expander 2 - Switching outputs:

The 8 bits of this port are intended for switching functions. The external wiring depends on the desired function. When switching higher voltages - in particular mains voltage - the relevant safety regulations are to be observed absolutely!

If a switching function is activated, then the level at the suitable output turns to low. The possible output current (sink) is typical 10mA, at maximum 25mA.

Bit 7 enables switching of the computer for automatic forwarding of faxes with full memory. Bit 6 switches on the current supply for the fax tone identificator only if this is required. Therefor the optional circuit is connected here instead of at J13 on the FAXCON board. A 80ms pulse on Bit 4 signals an identified tone from DLE string 2 in conjunction with fax switch type 2.

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         !    INITIAL MODE     !<----------------------------------+
         +---------------------+                                   !
         ! red !     green     !                                   !
         ! off !  fax number   !                                   !
         +---------------------+                                   !
            !                                                      !
            !            +----------------------+                  !
            +-- red ---->!     RECEIVE MODE     !------+-- red --->!
            !   short ^  +----------------------+      !   long    !
            !         !  ! red !     green      !      !           !
            !         !  ! on  !  fax number    !      !           !
            !         !  +----------------------+      !           !
            !         !                                !           !
            !         !  +----------------------+      v           !
            +         +--!    RECEIVING FAX     !<--- red          !
            !            +----------------------+     short        !
            !            ! red !     green      !                  !
            !            ! on  ! flashing fast  !                  !
            !            +----------------------+                  !
            !                                                      !
            !            +----------------------+                  !
            +-- green -->!     FORWARD MODE     !----------------->!
            !   long     +----------------------+                  !
            !            ! red !     green      !                  !
            !            ! off ! flashing fast  !                  !
            !            +----------------------+                  !
            !                                                      !
            !            +----------------------+                  !
            +-- red ---->!   DELETE FAX PAGES   !----------------->!
            !   long     +----------------------+                  !
            !            !  -  !       -        !                  !
            !            !     !                !                  !
            !            +----------------------+                  !
            !                                                      !
            !            +----------------------+                  !
            +-- green -->! LISTEN TO VOICECALLS !------------------+
                short    +----------------------+
                         ! red !     green      !
                         ! off ! flashing fast  !

Red led is on -> Receive mode or actual receiving of fax
Green led is flashing fast -> something happens
Deleting of Faxes is only possible after forwarding at least once
CONFIGURATION: push and hold green -> push red short -> release green

LEDs after power-up red green
memory test in progress on on
memory error occured blinking blinking

button pushed at power-up redgreen
generate testfax (push button >5sec -> 2 faxes) X
generate testfax and configure FAXCON automatically X
set FAXCON default configuration X X

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