Facsimile interface device for radios

Briefly, according to the invention, the interface device comprises matching device (20 and 22) for coupling a duplex information signal (21 and 23) to a simplex or a duplex radio (6) which provides a corresponding information signal (27) acknowledged by the half duplex or full duplex radio (6). Additionally, a signal detecting means (24) determines a desired signal strength and controls an interrupt signal (32). A means for sending (26) the interrupt signal (32) to the radio (6) sends the interrupt signal once the signal detecting means detects the desired signal strength. Finally, the interface device of the present invention comprises a means for sending (26) the corresponding information (27) once the interrupt signal is sent.

TECHNICAL FIELD 
This invention relates generally to the field of facsimile interface 
devices for communication devices, and more specifically to a device for 
connecting a facsimile device to either a full duplex or simplex radio. 
BACKGROUND 
Conventional interfacing devices for transmission of duplex information 
allows for receipt of the information by full-duplex radios such as 
cellular phones. The increasing demand for installation of facsimile 
devices (which typically provide full-duplex information) in motor 
vehicles which have typical mobile radios may be precluded from receiving 
facsimile transmissions because their radio systems are not full duplex, 
but rather half-duplex or simplex. The previous solution to this problem 
would be to simply provide for a separate duplex radio or otherwise 
receive a non-standard simplex fax. Another solution includes using a 
non-standard fax machine that would have control lines linking with the 
interface device for controlling the receive and transmit mode. The 
present invention eliminates these restraints by providing an interface 
between the duplex signals of a standard telephone type FAX machine and a 
half-duplex radio. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
facsimile interface device for duplex to simplex radio communication 
Briefly, according to the invention, the interface device comprises 
matching means for coupling a duplex information signal to a simplex or a 
duplex radio which provides a corresponding information signal 
acknowledged by the half duplex or full duplex radio. Additionally, a 
signal detecting means determines a desired signal strength and controls 
an interrupt signal. A means for sending the interrupt signal to the radio 
once the signal detecting means detects the desired signal strength. 
Finally, the interface device of the present invention comprises a means 
for sending the corresponding information once the interrupt signal is 
sent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a block diagram of the present 
invention. A conventional duplex FAX machine such as Facsimile Machine 2 
sends duplex information signals (8) to a facsimile interface device 4. 
The facsimile interface device 4 provides for impedance, voltage and 
current matching as is known in the art between the Facsimile Machine 2 
and a half duplex radio 6. The device 4 sends and receives transmit and 
receive audio along with control signals including an interrupt signal 
which functions as a push to talk (PTT) switch. The interrupt signal is 
generated from within the device 4 in response to the audio signal from 
the facsimile machine 2, rather than from control signals from a fax 
machine as is known in the art. In other words, the facsimile interface 
device 4 examines the (audio) Fax transmission (8) from the Facsimile 
machine 2 and determines when the half duplex radio 6 should be 
transmitting (via antenna 7). Even though the the Facsimile machine 2 
interfaces via a duplex connection, the interface device 4 is able to 
determine when to transmit since the data transmissions are simplex, with 
sufficient time between receiving and transmitting data for the radio to 
start transmitting. During this time, the device 4 activates the half 
duplex radio's (6) PTT line. Otherwise, the half duplex radio 6 is 
receiving at all other times. 
Referring to FIG. 2, there is shown the facsimile interface 4 connecting 
one facsimile machine (2) to another facsimile machine (54) via two half 
duplex radios (6 and 50) each having antennas (7 and 51 respectively.) An 
RJ-11 circuit 20, coupled to a duplex signal source such as facsimile 
machine 2 receives a ring and tip signal on lines 21 and 23 respectively. 
The 2 to 4 wire convertor 22 receives a telephone line matched signal 25 
from the RJ-11 circuit and provides separate radio Receive and Transmit 
audio signals. The 2 to 4 wire conversion can be done using Motorola's 
integrated circuit parts MC34014 and MC3419. 
A facsimile signal comparator/detector 24 comprises a signal detector, a 
comparator and a Push-To-Talk (PTT) generating circuit. In one embodiment 
of the present invention, the comparator will look for sufficient energy 
from the detector to cause the radio 6 to start a transmission of the FAX 
data. When the energy falls below a lower threshold, the radio 6 will stop 
transmission. Since facsimile machine modulation uses a phase modulated 
carrier, the energy content of the carrier will remain relatively constant 
during the data transmission and the radio will not de-key until the 
transmission has been completed. No carrier signal is generated by the 
facsimile machine during receive. 
In an alternative embodiment of the present invention, the 
detector/comparator 24 will actually decode the data being sent by the 
facsimile machine 2 and determine when to transmit or receive. Numerous 
integrated circuits are available (Yamaha YM7109 for example) that can 
demodulate Fax data. Using this approach will prevent any possible falsing 
problems that could occur using the energy detection approach described 
above. 
In either embodiment, when the detector/comparator 24 determines that the 
radio 6 should be transmitting, radio circuitry 26 should mute the radio 
microphone audio, activate the radio PTT and route the Fax machine audio 
(30) to the radio modulation circuitry (6). When the facsimile interface 4 
receives fax information from another facsimile machine (54), the receive 
audio should be routed to the facsimile machine 2 through the 2 to 4 wire 
convertor 22. The radio speaker in the half duplex radio 6 should also be 
muted during a Fax reception. 
Implementing the alternative embodiment (using the (Yamaha YM7109 for 
example) would increase the flexibility of fax machines and provide 
additional features since the interface 4 could examine the data being 
sent to the facsimile machine 2. Such features include the group wide Fax, 
wherein a Fax transmission sent over a radio channel could be sent to 
multiple users at the same time without a significant increase in required 
RF airtime. A destination ID (typically the telephone extension) would be 
required for each user. An Acknowledgement feature would provide the 
sending party notice that the receiving party actually picked up the Fax. 
This could be done by either sensing the page being removed or the 
operator manually pressing a button on the receiving Fax machine. The 
Acknowledgement feature would save the normal step of calling the 
receiving party to determine if the Fax was received correctly. Another 
feature, Page On Receipt could have the radio system automatically page 
the receiving party when the Fax was received. The receiving radio could 
automatically page the user or tie into a separate paging system using the 
radio ID or telephone number to which the Fax was sent once the Fax 
transmission triggers the paging system.