JPH11261755A - Data access arrangement(daa) device in secure fax adaptor and method for connecting transmission data to facsimile equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the DAA system in the compact, light weight and inexpensive secure FAX adaptor very flexible in the operation constitution. SOLUTION: The system is constituted of an off-hook detection circuit 301 having an input to be coupled with a FAX communication circuit 201 and an output to be coupled with a controller 220, a ring detection circuit 303 having an input and an output to be coupled with the FAX communication circuit 201, a ring generation circuit 305 having an input to be coupled with a microprocessor and an output to be coupled with the ring detection circuit 303, and a relay circuit 302 having plural control inputs to be coupled with the controller 220, a port to be coupled with an external device port, a port to be coupled with the FAX communication circuit 201, a port to be coupled with the off-hook detection circuit 301, a port to be coupled with the ring generation circuit and takes plural operating states in response to the control inputs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile (fax) device, and more particularly to a data access arrangement (DAA) device in a fax adapter device and a facsimile connection method for connecting transmission data to a facsimile.

[0002]

2. Description of the Related Art One conventional fax machine is a PSTN.
Non-secure data is transmitted / received via the Public Switched Telephone Network (public telephone line) using the G3 fax communication protocol. Certain other fax machines send and receive secure data over a secure network using a secure protocol such as the STU (Secured Telephone Unit) protocol.
In recent years, the cost of G3 fax machines has dropped,
3 fax machines are available in large quantities. However, these conventional G3 fax machines cannot directly connect to the STU. In some cases, it is desirable to couple a conventional G3 fax machine to a secure network via an STU. In these cases, the secure fax adapter sets the conventional G3 fax machine to ST
Used to couple to U.

[0003] Secure fax adapters have several TCOs, including off-hook detection and ring generation.
To achieve the (Telephone Central Office) function, DAA (Data Access Arrangement) is usually used. Conventional DAA off-hook detection circuits measure the voltage drop across the load to determine on-hook / off-hook. Conventional off-hook detection circuits do not provide sufficient current limiting to prevent devices coupled to the secure fax adapter from being damaged or becoming incompatible. Moreover, conventional off-hook detection circuits include diodes in the path of the detection signal that have an undesirable effect of introducing distortion into the detection signal. Ring generation (bell sound generation)
Is another TCO function typically performed by the Secure Fax Adapter-DAA. Some conventional adapter DAAs use a transformer to generate a sinusoid for ring generation.

[0004]

However, as mentioned above, the use of transformers is not preferred because of increased cost, weight and size. Thus, there is a need for a low cost, light weight, and compact secure fax adapter that has enhanced DAA with improved ring generation and off-hook detection, and that has increased operational configuration flexibility. SUMMARY OF THE INVENTION It is an object of the present invention to provide a DAA device and a method for connecting transmission data to a fax in a low-cost, lightweight and compact secure fax adapter with increased flexibility in operation configuration in view of the above circumstances.

[0005]

SUMMARY OF THE INVENTION To achieve the above objects, an enhanced DAA device of the present invention has improved off-hook detection, ring generation, and configuration flexibility. The enhanced DAA has a signal port for coupling to a fax communication circuit, an external device port including an STU port and a G3 fax port, an off-hook detection circuit, a ring detection circuit, a ring generation circuit, and a relay circuit.

The relay circuit has a G3 fax port,
In accordance with a control signal received from the controller, it is configured to be selectively coupled to one of an STU port, a fax communication circuit, and a ring generation circuit. In one embodiment, the controller is a CPU (Cen
tral Processing Unit). In another embodiment, D
AA also has a PST for coupling to the PSTN line.
Has N ports. In this embodiment, the relay circuit further controls the STU port in response to a control signal received from the controller by a fax communication circuit or a PST.
Connect to N port.

In another embodiment, the off-hook detection circuit has two sensing nodes and a current limiting circuit coupled to the sensing circuit to produce a logic signal that matches the signal detected at the sensing node. The output of the detection circuit is a logic signal indicating either on-hook or off-hook detection for coupling to the controller. The current limiting circuit has a symmetric current limiter. It is for the sensing node. The current limiters each have a transistor having a base electrode coupled to a power source through a diode to limit the current flowing to the load through the transistor. The current limiting circuit is coupled to a detection circuit that generates a logic signal indicating on-hook / off-hook detection. This logic signal is coupled to the controller.

In another embodiment, the ring generator has a pair of switch circuits and generates a square wave ring signal. The first switch circuit has a non-inverting adjustment circuit that receives a square wave having a desired frequency from the controller. The output of the non-inverting adjustment circuit is coupled to a push-pull amplifier for generating an amplified square wave that matches the frequency of the square wave received from the controller. The second switch circuit has an inversion adjusting circuit that receives a rectangular wave from the controller. The output of the inverting adjustment circuit is coupled to a push-pull amplifier for generating an amplified inverted square wave that matches the frequency of the square wave received from the controller.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a secure fax adapter device according to one embodiment of the present invention, a relay circuit is provided for selecting a G3 fax as a secure line via a secure telephone unit (STU) and securing (protecting) it. Used. The G3 fax is selectively coupled to the public switched telephone network (PSTN) via the PSTN port.

[0010] The secure fax adapter has an extended DAA, which includes a controller, a fax communication circuit, a current control off-hook detection circuit, a relay circuit for selecting and controlling an external device port, and a rectangular for ring generation. It has a ring generation circuit for generating waves. In one embodiment, the current controlled off-hook detection circuit uses a symmetric network of transistors coupled to a diode to limit the current drawn by the load.

The relay circuit (302) has four relays. The G3 fax (101) is used for the fax communication circuit (201), the STU (102) is used for the PSTN,
G3 fax (101) to PSTN,
The STU is selectively coupled to a fax communication circuit. The relay circuit includes an auxiliary relay for coupling the off-hook detection circuit (303) to the fax communication circuit (201).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a secure fax adapter (SFXADP) 100 for coupling a G3 fax 101 to an STU 102 in the present invention.
SFXADP 100 has a variety of user-selectable path configurations to adapt conventional G3 fax 101 to STU 102.

SFXADP100 is a G3 fax 1
01, STU102, personal computer 103,
It has a PSTN (telephone subscriber line) port 105 and external device ports 110-115 for coupling to conventional external devices including a power supply module 104. Port G
110 couples SFXADP 100 to conventional G3 fax 101. Also, instead, SFXADP
100 port G110 is the CCIT of port G110.
It may be coupled to a modem or other device that conforms to the TG3 protocol.

In a preferred embodiment, port G110
Is a standard telephone subscriber line interface circuit (SLIC) consisting of two wires, a data chip (DT) and a data ring (DR) wire. Port S112
Couples SFXADP 100 to a secure communication device such as STU 102, and port H111
100 is coupled to a host such as a personal computer 103.

Port P114 is an auxiliary telephone port that can be internally coupled with port L113 to form a general PSTN port. In a preferred embodiment, ports S112 and H111 are RS-232C ports. The power supply module 104 is an SFXADP100
Power input port 115.

Further, the STU 102 has a dedicated line 106
Combined with Instead, the conventional STU 102
It may be coupled to TN or recoupled to SFXADP 100 via port P114. In a preferred embodiment, port P114 and port L11
3 are RJ1 with DT and DR wires, respectively
One port.

FIG. 2 shows an SFXADP10 according to the present invention.
0 is a block diagram. SFXADP100
Receives the timing signal from the oscillator 214 and
Programmable read-only memory (EPROM) 2
16 and static random access memory (SRAM) 217
And a controller such as a central processing unit (CPU) 220 for controlling fax communication by transmitting and receiving control commands to and from the MFP. In a preferred embodiment, CPU 220 is an Intel 80C188XL.

A standard erase / programmable logic device (EPLD), such as a model EP1810 integrated circuit
204 communicates with a CPU (controller) 220, and serial communication controllers (SCC) 205 and 206, and a fax chip set (fax communication circuit) 2
01 is controlled.

The fax chip set 201 is a fax communication circuit using a conventional fax protocol. In a preferred embodiment, fax chipset 201 is a model RC96V24AC fax chipset produced by Rockwell.

SCCs 205 and 206 are serial communication controllers, such as a commercially available model AM85C30 produced by the Advanced Micro Devices of Sunnyvale, CA. The SCCs 205 and 206 convert transmission data from a parallel data format to a serial data format, and convert data received from either the secure fax network or the PSTN from a serial data format to a parallel data format.

At the time of transmission, the fax chip set 201
Transfers data to the data bus 203. SCC20
5 receives parallel data from the data bus 203,
After conversion into serial data, the data is transferred to the transceiver 207. Thereafter, the transceiver 207 transmits the serial data to the port S112 for coupling to the STU 102.
Send to CPU (controller) 220 and SC
C205 sets up automatic synchronization words, baud rate detection, and network information exchange for all standard secure fax protocols, preferably embedded or stored in EPROM 216.

Similarly, SCC 206 is connected to data bus 20
3 receives the parallel data, converts it into serial data, and then transfers it to the transceiver 210. Transceiver 210 has a port H11 for coupling the serial data to personal computer (PC / AT) 103.
Send to 1. CPU (controller) 220 and SCC
205 and 206 set up automatic synchronization words, baud rate detection, and network information exchange for all standard PC / AT protocols, preferably embedded or stored in EPROM 216.

The CPU (controller) 220 transmits and receives address information via the internal address bus 218.
Internal address bus 218 is coupled to data bus 203 for receiving address information, and
5 is connected to the address bus 2 according to a control command received from the CPU (controller) 220.
Erasable / programmable ROM (EPROM) as storage means including protocol software via 19
216 or a static random access memory (SRAM) 217 as a storage means.

In a preferred embodiment, the EPROM 21
6 stores a 256K 8-bit word,
17 stores 512K 8-bit words. CPU
As the (controller) 220 controls the memory read / write function, the data bus 203 also
Combine the data to both M216 and SRAM 217.
The address bus 219 further transmits control information to the CPU.
(Controller) 220 to EPLD 204, SCC2
05 and 206, to the fax chip set 201.

The CPU (controller) 220 sends control commands to the EPLD 204, EPROM 216, SRAM2
17, DAA200, fax chip set 201,
SCC 205 and 206, LCD (Liquid Crystal Display) 2
12 and the mode switch 213.

FIG. 3 shows a DAA enhanced according to the present invention.
20 is a block diagram of a 200. DAA200
Is the fax switch set interface port 2
02, external device ports 221, 222, 223, off-hook detection circuit 301, relay circuit 302, ring detection circuit 303, ring generation circuit 305, PST
It has an N-line interface 304.

[0027] Relay circuit 302 is coupled to device ports 222 and 223 and to device port 221 via PSTN line interface 304. The relay circuit 302 further supplies the ring detection circuit 303 and the generation circuit 305 with the off-hook detection circuit 30.
1 and interface port 202.

FIG. 4 shows a DAA enhanced according to the present invention.
FIG. FIG. 4 is a schematic diagram showing an off-hook detection circuit 301, a relay circuit 302, a ring detection circuit 303, and a PSTN line interface 30.
4 shows a schematic diagram of FIG.

FIG. 5 is a schematic diagram of the relay circuit of the DAA 200. The relay circuit 302 includes relays 401 to
405 and a split transformer 407. The split transformer 407 is connected via the interface port 202 to
It has a receiving node (RX) and a transmitting node (TX) for coupling to the fax chipset 201. 4 and 5, each of the relays 401 to 405 is turned off when the contact C is connected to the upper opposed contact NC.
FF, ON when connected to the lower opposing contact NO
And

Table 1 shows the relationship between the state of the relays 401 to 405 and the connection configuration. In a preferred connection configuration as shown in Table 1, relays 401-405 electrically couple external device ports 221, 222, 223, fax chipset interface port 202, ring generation circuit 305, and off-hook detection circuit 305.

[Table 1]

In operation, relays 401-405 are configured to provide the desired electrical coupling. In the non-operational mode (first connection configuration a), all relays are off and therefore relay 402 couples TX and RX nodes to port G110, which is adapted to couple to a G3 fax machine. . Thus, in the non-operation mode,
The RX and TX signals of the fax chipset 201 are G
3 Fax 101

In the second connection configuration b, the relay 403 is on, and the relays 401, 402, 404, and 405 are off. This couples port S112 (adapted to couple to STU 102) with port L (adapted to couple to PSTN line 105). This second connection configuration b is selected when there is only one single PSTN line available for transmitting and receiving data from the single PSTN.

In the third connection configuration c, the relay 404 is on and the relays 401 to 403 and 405 are off. In this connection configuration c, port G110 (adapted to couple to G3 fax 101) is coupled to port L113 (adapted to couple to PSTN line 105). This third connection configuration c is selected when a bypass of the SFXADP 100 is required during operation.

In the fourth connection configuration d, the relay 405 is on and the relays 401 to 404 are off. In the fourth connection configuration d, the SFXADP 100 has a “wake-
selected in the “up” mode. The relay 405 is connected to the G3
The fax 101 is switched on to insulate the fax 101 from the RX and TX lines, and instead couple the ring generation circuit 305 (comprising a double switch) to the G3 fax 101 via port G110.

In the fifth connection configuration e, the relays 403-4
05 is off and only relays 401-402 are on. This fifth connection configuration e couples port H111 (adapted to be coupled to personal computer 103) to fax chipset 201.

Returning to FIG. 4 again, the offset detection circuit 301 includes the detection nodes PV326 and NV327, the symmetric current limiting circuits 340 and 341 and the detection circuit 34.
2 The sensing nodes PV 326 and NV 327 are coupled to a load such as G3 fax 101 via port G110.

The current limiting circuit 340 includes the transistor 31
0, a resistor 315, and a Zener diode 314. Current limiting circuit 341 includes a transistor 313, a resistor 322, and a Zener diode 328. Transistors 310 and 313 are current limiting regulators for supplying positive and negative currents, respectively. Zener diodes 314 and 328 are coupled to respective current supply transistors 310 and 313 to limit the supplied current to 16 mA.

By limiting the current supplied by the off-hook detection circuit 301, external equipment and devices are safely guarded against damage. The off-hook detection circuit 301 includes input voltage nodes 324 (+12 volts) and 325 (−12 volts) and a detection node PV32
6, limiting current by creating a high impedance between the load coupled to NV327.

The off-hook detection circuit 301 includes resistors 316 to 318 and 320 to 321 and a transistor 31
1 to 312 and a detection circuit 34 having a capacitor 323
Contains 2. The detection circuit 342 detects the detection node PV3
26 and a logic signal PHNOH indicating whether NV327 is “off-hook” detection or “on-hook” detection.
/ 329 is generated.

When G3 fax 101 is "off hook", sensing nodes PV 326 and NV 327 have a load of 600 ohms, thereby being pulled to "low",
Transistors 310 and 313 are turned on. However, the current flow (source) to the load is limited using zener diodes 314 and 328. Zener diodes 314 and 328 are 2.4
Can withstand the maximum voltage drop of volts. As a result, the sense node PV32 through the transistors 310 and 313
6 and the current flowing to NV327.

The maximum voltage drop across resistors 315 and 322 is the maximum voltage drop that can be tolerated by zener diodes 314 and 328 from transistors 310 and 31.
3 is equal to the value obtained by subtracting the base-emitter voltage drop.

The emitter current Ie of transistors 310 and 313 corresponds to the current drawn by the G3 fax 101 load. Thus, the load current is equal to the current flowing through resistors 315 and 322, respectively, which is limited by Zener diodes 314 and 328. When transistors 310 and 313 are in the "on" state, transistors 311 and 312 are also "on", causing the PHNOH / 329 line to be "low" indicating that the load is "off-hook".

G3 fax 101 is "on hook"
, The sensing nodes PV 326 and NV 327 have a high resistance impedance,
6 and NV327 remain "high". When the sensing nodes PV 326 and NV 327 are “high”, the transistors 310 and 313 cause the negligible collector current I
c, it is in the “off” state.

The collector voltage of transistor 310 is essentially the same as the base voltage of transistor 311;
Further, since the resistor 316 has a higher resistance than the resistor 315, the emitter voltage of the transistor 311 is lower than its base potential, and the transistor 311 is in the “off” state with negligible current. Transistor 313 is similarly biased to an "off" state.

Since only negligible current flows through the resistors 317 and 320, the transistor 312 is biased to the "off" state, and the logic signal PHNOH / 329 indicating that the load is "on-hook" becomes "high". So that

DAA 200 further has a ring detection circuit 303 in addition to off-hook detection circuit 301. The ring detection circuit 303 is coupled to the relays 402 and 403, and is connected to the port S112 (STU port) or the port L113.
(PSTN line) is detected. The ring detection circuit 303 requires less power than the conventional ring detection circuit. The power consumption of the ring detection circuit 303 is 18 volt Zener diodes 330 and 332 and the switching diode 3
Reduced by using 31.

A ring signal greater than 18 volts DC
Trigger the threshold of the opto-isolator 333. Opto-isolator 333 couples signals of the same frequency to fax chipset 201. By using Zener diodes 330, 332 and switching diode 331 to condition the ring signal and using an opto-isolator 333 to couple the ring signal to fax chipset 201, the need for a high voltage ring signal is required. Is gone.

FIG. 6 is a diagram for explaining ring generation circuit 305 according to the present invention. Ring generation circuit 305 generates a set of square wave ring signals 530 and 531 for coupling with G3 fax 101.

As mentioned above, since the ring detection circuit 303 of the present invention does not require a traditional high voltage ring signal, the ring generation circuit 305 does not require a large and heavy step-up transformer. Instead, the ring generation circuit 305 of the present invention uses + 12V
Transistor double switching circuits 510, 511 are used to generate a set of square wave ring signals 530 and 531 having a voltage amplitude between and -12V.

The ring generation circuit 305 generates an absolute voltage of 24V (amplitude between + 12V and -12V) sufficient to start the ring detection circuit 303.
In addition, the frequency of the pair of ring signals 530, 531 is
Controlled by microprocessor 220 to accommodate various foreign G3 fax requests. The ring generation circuit 305 receives the input signal FREQ5
32, and generates a set of ring signals 530 and 531 to drive the ring detection circuit 303.

In a preferred embodiment, the input signal FRE
Q532 is a 5V square wave at a 20Hz frequency (according to North American telephone standards), and ring signals 530 and 5
One set of 31 is a square wave having an absolute voltage of 24V (amplitude of 24V).

The ring generation circuit 305 includes two
Includes two complementary switching circuits 510 and 511. The switching circuit 510 includes a driving circuit 512 and a non-inverting circuit 513. Drive circuit 512 is a push-pull follower amplifier, and includes an NPN transistor 521 connected in series with PNP transistor 522. The base electrodes of transistors 521 and 522 are common and are coupled to the collector electrode of transistor 523.

Similarly, the switching circuit 511 has a drive circuit 514 and an inversion circuit 515. Drive circuit 514
Is a push-pull follower amplifier, and an NPN transistor 52 connected in series with a PNP transistor 526.
5 is included. The base electrodes of transistors 525 and 526 are common and are coupled to the collector electrode of transistor 527.

Drive circuits 512 and 514 are set to + 12V
And a -12V voltage supply. Drive circuits 512 and 514 respectively generate a set of ring signals 530 and 531 having rectangular waves swinging to opposite voltages.

In operation, non-inverting circuit 513 uses transistors 524 and 523 to adjust received frequency signal FREQ 532. The output of non-inverting circuit 513 is coupled to drive circuit 512.

When FREQ 532 is “1” or “hig”
At time h "(when the signal has a voltage greater than or equal to the threshold voltage required to turn on transistor 524), transistor 524 conducts and transistor 523 is turned on so that transistor 523 also conducts.

On the contrary, if FREQ 532 is “0” or “l”
ow ", the transistors 524 and 52
3 turns off and does not conduct. The output of transistor 523 drives transistor pair 521 and 522 to generate in-phase FREQ 532.

That is, FREQ 532 is "high"
Then, the output of the non-inverting circuit 513 becomes “high”, and the output of the driving circuit 512 also becomes “high”.
become. Conversely, if FREQ 532 is "low", the output of non-inverting circuit 513 will be "low" and the output of drive circuit 512 will also be "low".

Similarly, the switching circuit 511 inverts and amplifies the received input signal (FREQ 532). The inverting circuit 515 includes transistors 527, 528,
529 is used to invert FREQ 532 and drive circuit 5
To 14 The inverting circuit 515 includes a non-inverting circuit 513.
, A transistor 529 for inversion is added to the preceding stage.

In operation, if FREQ 532 is "low", the output of inverting circuit 515 will be "high".
h ”, and the output of the driving circuit 514 also becomes“ h ”.
FREQ 532 becomes “high”
If so, the output of inverting circuit 515 goes "low" and the output of drive circuit 514 also goes "low".

In operation, the user has a G3 fax 1
When transmitting using 01, the G3 fax 101 switches from an "on-hook" state to an "off-hook" state. In response to this change in state, the off-hook detection circuit 30
1 detects that the G3 fax 100 is "off-hook" and indicates that the G3 fax 100 is in an off-hook state by a logic signal P
Fax chipset 2 using HNOH / 329
Notify 01.

The CPU (controller) 220 configures the DAA 200 in response to the fax chip set 201 receiving the “off-hook” indication by the logic signal PHNOH / 329, and the fax chip set 201
To receive and retransmit data.

However, if the G3 fax 10
If 1 is in the “on-hook” state and SFXADP 100 receives an external transmission, SFXADP 100
To place the G3 fax 101 in a state of receiving the transmitted data, the G3 fax 101 is set to “wak”.
e-up ".

SFXADP generates a ring signal to make the G3 fax 101 “wake-up”. Upon receiving the ring generation “wake-up” signal, the G3 fax 101 changes from the on-hook state to the off-hook state.

When the off-hook detecting circuit 301 detects that the G3 fax 101 is in the "off-hook" state, it outputs the "off-hook" signal by the logic signal PHNOH / 329.
The fax communication circuit 201 is notified of the status. "Off hook" by logic signal PHNOH / 329
Fax chipset 2 notified of status
In response to 201, the CPU (controller) 220 reformats the received external transmission and combines the reformatted data with the G3 fax 101,
The DAA 200 is configured.

[0066]

According to the present invention, it is possible to provide a DAA device in a low-cost, light-weight, and compact secure fax adapter with increased flexibility in operation configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram of a secure fax adapter that couples a G3 fax and an STU according to the present invention.

FIG. 2 is a block diagram of a secure fax adapter according to the present invention.

FIG. 3 is a block diagram of an enlarged DAA according to the present invention.

FIG. 4 is a schematic diagram of an enlarged DAA in the present invention.

FIG. 5 is a schematic diagram of a relay circuit according to the present invention.

FIG. 6 is a schematic diagram of a ring generation circuit according to the present invention.

[Explanation of symbols]

100: Secure fax adapter (SFXAD)
P), 101: G3 fax, 102: STU (Secured Telephone Unit), 103: personal computer (PC / AT), 104: power supply module, 105: PSTN (telephone subscriber line) port, 106: dedicated line, 110, 111, 112, 113, 114, 115: external device port 110, 200: DAA (Data Access Arrangement), 201: fax chip set (fax communication circuit), 202: fax switch set interface port, 203: data bus, 204: Erasable / Programmable Logic Device (EPL
D), 205, 206: Serial communication controller (SC)
C), 207, 210: transceiver, 212: LCD (liquid crystal display), 213: mode switch, 214: oscillator, 215: latch, 216: EPROM, 217: SRAM, 218: internal address bus, 219: address bus, 220: CPU (controller), 221, 222, 223: external device port, 301: off-hook detection circuit, 302: relay circuit, 303: ring detection circuit, 304: PSTN line interface, 305: ring generation circuit, 310, 311 312, 313: transistor, 314, 328, 330, 332: Zener diode, 315, 316, 317, 318, 320, 321, 3
22: resistor, 323: capacitor, 324, 325: input voltage node, 326, 327: detection node, 329: logic signal (PHNOH /), 331: diode, 333: opto-isolator, 340, 341: current limiting circuit, 342 : Detection circuit, 401, 402, 403, 404, 405: relay, 407: split transformer, 510, 511: switching circuit, 512, 514: drive circuit, 513: non-inverting circuit, 515: inverting circuit, 521, 522 , 523, 524, 525, 526, 5
27, 528, 529: transistors; 530, 531: rectangular wave ring signal; 532: input signal FREQ.

Claims (9)

[Claims] 1. A fax communication circuit (fax chip set 201), a controller (CPU 220),
A data access arrangement (DAA) device (200) for a fax adapter having a plurality of external device ports, the DAA device (200) comprising an input coupled to a fax communication circuit (201) and a controller (220). An off-hook detection circuit (301) having an output coupled to a fax communication circuit (201); a ring detection circuit (303) having an input and an output coupled to a fax communication circuit (201); and an input coupled to a controller (CPU 220). A ring generation circuit having an output coupled to the ring sensing circuit; a plurality of control inputs coupled to the controller; a first plurality of interface ports coupled to the external device port; , A second coupled to a fax communication circuit
A plurality of interface ports, one interface port coupled to the off-hook detection circuit (301), and one interface port coupled to the ring generation circuit, and a plurality of operations in response to the plurality of control inputs. A DAA device (200), comprising: a relay circuit (302) for taking a state. 2. The DAA device (200) according to claim 1, wherein the interface port is a fax port (22).
3) and a secure telephone unit (STU) port (222), wherein the relay circuit (302) is comprised of first to fourth relay circuits, and the first relay (401) is a fax communication circuit. (20
A first port coupled to the fax communication circuit (301) coupled to an off-hook detection circuit (301) and responsive to at least one of the plurality of control inputs;
And a second port for selectively coupling 1) to the off-hook detection circuit (301). The second relay (405) includes a first port, a second port, and a ring generation circuit (301). 305) coupled to at least one of the plurality of control inputs, wherein the first port is selected as one of a second port and a ring generation circuit (305). The third relay (404) has a fax port (22).
3), a second port coupled to the first port of the second relay (405), a third port, and at least one of the plurality of control inputs. Ring generation circuit (305) according to one
To a fax port (223), and a fourth relay (403) is connected to the first port and the third port.
A second port coupled to a third port of the first relay (404) and a third port coupled to the STU port (222); and a fifth relay (402) for fax communication. A first port coupled to a circuit, a second port coupled to a second port of the second relay (405), and a first port coupled to a fourth port of the fourth relay (403). A third port for selectively coupling a fax communication circuit to the STU port (222) and selectively coupling the fax communication circuit to the fax port in response to at least one of the plurality of control inputs. DA
A device. 3. The DAA device according to claim 2, wherein said interface port further comprises a PSTN line port coupled to a first port of a fourth relay (403). 4. The DAA device according to claim 2, wherein said off-hook detection circuit is a current limiting circuit. 5. The DAA device according to claim 4, wherein the off-hook detection circuit including the current limiting circuit has first and second detection nodes, and a collector electrode, an emitter electrode, and a base electrode. Is coupled to a first sensing node, the emitter electrode is coupled to a first voltage terminal via a first resistor, and the base electrode is coupled to the first voltage terminal via a first diode. A first current limiting transistor, a collector electrode, an emitter electrode, and a base electrode, the collector electrode being coupled to the second sensing node, and the emitter electrode being connected to a second voltage through a second resistor. A second current limiting transistor coupled to the terminal, the base electrode being coupled to the second voltage terminal via a second diode; and an emitter of the first transistor. A sensing circuit having a first input combined, a first logic state indicating that the sensing node is off-hook, and an output having a second logic state indicating that the sensing node is on-hook. A DAA device comprising: 6. The DAA device according to claim 2, wherein the ring generation circuit has a rectangular wave generation circuit. 7. The DAA device according to claim 6, wherein said square wave generating circuit comprises: an input node coupled to a controller for receiving a square wave; A first switching circuit comprising a non-inverting signal state circuit for adjusting and an amplifier coupled to the non-inverting signal state circuit for generating an amplified and adjusted square wave; A second switching circuit comprising an inverted signal state circuit for inverting and adjusting the amplified square wave and an amplifier coupled to the inverted signal state circuit for generating an amplified and inverted square wave. A DAA device, characterized in that: 8. A fax combining method for combining transmission data with a fax having an off-hook state and an on-hook state, the method comprising: generating a square wave fax wake-up signal; After combining a wake-up signal with the fax, monitoring the fax for an off-hook condition, and combining the transmission data with the fax in response to the detection of the off-hook condition. 9. The method of claim 8, wherein the step of monitoring the fax to detect the off-hook condition comprises: coupling a power supply via first and second fax detection nodes. To the fax; limiting the current supplied to the fax; generating a status signal corresponding to the first and second power levels at the first and second fax sensing nodes. And a fax combining method.