Abstract:
The controlled electromagnetic induction detonation system for initiation of a detonatable material system includes an automated radio charge (ARCH) module connectable to an electric detonator, a transducer module for providing operational power by electromagnetic induction to the ARCH module, and a remote controller for sending instructions to the transducer module from a location remote from the detonator. Upon completion of an arming sequence, the transducer module generates an electromagnetic field which is picked up by a coil in the ARCH module and used to power the ARCH module and provide a detonation current for the detonator. The transducer module or at least a coil thereof which produces the electromagnetic field is supported on or in a stemming bar which in turn acts as a core of an electromagnet confining the magnetic flux for pick up by the ARCH module. Multilevel access control and interlock systems operate between the remote controller, transducer unit and the ARCH module to reduce the likelihood of unintentional initiation of the detonator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority, under 35 U.S.C. § 365 (a), to PCT Patent Application Ser. No. PCT/AU98/00929, filed on Nov. 6, 1998, and published in English on May 20, 1999 as WO 99/24776, which claims priority to Australian Patent Application Ser. No. PP 2016, filed on Nov. 6, 1997 the entirety of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a controlled electromagnetic induction detonation system for initiation of a detonatable material, and in particular, but not exclusively, for decoupled in-hole initiation of a detonatable material. 
     BACKGROUND OF THE INVENTION 
     Throughout this specification and claims the term “detonatable material” is used in a broad and generic sense to include any initiating device such as an electrical detonator, fuse, fusehead, electric match; and, any energetic material such as explosive, propellant and the like. 
     Explosives and propellants are used in the mining and construction industries in many different applications including tunnelling, stoping, civil excavations and boulder breaking. 
     In order to initiate the explosive or propellant some type of detonator or fuse is required. The detonator or fuse in turn can be set off either electrically or mechanically. The present invention is concerned with the wireless electric initiation of a detonator or fuse or other energetic material. 
     Most commonly, the initiating of an electric detonator or fuse is accomplished by a physical conductor such as a wire pair connected at one end to the detonator and at an opposite end to an electric power supply via a switch. When the switch is closed, current flows through the wire to initiate the detonator or fuse. 
     Such type of electric initiation system can sometimes be set off prematurely or accidentally through the induction of electric currents in the conductors by stray electromagnetic fields or, through faults in the initiating electric circuit comprising the wires, switch and power supply. 
     Another electric initiation system available under the brand name Magne-Det is known in which a pair of electric conductors that are attached to a detonator extend through a coil through which a current flows. The current flowing through the coil induces a current to flow through the conductors which in turn is used as the detonation current. However this system is also clearly prone to accidental or premature activation by picking up stray electromagnetic fields. 
     All of these initiation systems require manual connection of the detonator to a source of initiation energy. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a detonation system in which the likelihood of accidental initiation of a detonatable material is substantially reduced. It is a further object of the present invention to provide a system for wireless non-contact initiation of a detonatable material. 
     According to the first aspect of the present invention there is provided a controlled electromagnetic induction detonation system for initiating a detonatable material, the system including: 
     an automated radio charge (ARCH) module for delivering an electric detonation current to a detonatable material, said ARCH module having no permanent on board power supply including a power circuit for extracting power by means of electromagnetic induction from a electromagnetic field generated remotely from the ARCH module, the power circuit providing operational power for the ARCH module and the electric detonation current, and means for receiving and decoding radio transmitted control signals including a FIRE code, the verified receipt of which causes the ARCH module to deliver said current to and thereby initiate the detonatable material. 
     Preferably the means for receiving and decoding the control signal extracts the control signal from said electromagnetic field. 
     Preferably said control signal includes an ARM code and the means for receiving and decoding, upon receipt, decoding and verification of said ARM code, initiates a timer in said ARCH module to time a predetermined period in which said ARCH module must receive, decode and verify said FIRE code in order to deliver said detonation current to the detonatable material, and in the absence of which, said ARCH module automatically shuts down for a second predetermined period. 
     Preferably said ARCH module further includes an output switch through which said electronic detonation current must flow in order to initiate the detonatable material, said switch configured to provide a short circuit output to the detonatable material until receipt and verification of said FIRE code, in which instance, said switch is operated to remove said short circuit and allow the electronic detonation current to flow to the detonatable material. 
     Preferably said system further includes a transducer unit having a power supply for supplying power to electromagnetic field generating means for generating said electromagnetic field and radio transceiver means for radio transmitting said control signals to the ARCH module. 
     Preferably said transducer unit further includes means for impressing said control signals onto said electromagnetic field so that said radio transceiver means transmits both said electromagnetic field and said control signals to said ARCH module. 
     Preferably said transducer unit includes a mode switch switchable between a LOCAL mode and a REMOTE mode of operation, wherein in said LOCAL mode of operation, a user can manually input instructions to said transducer unit for radio transmission to said ARCH module and wherein in said REMOTE mode of operation, a user can input instructions to said transducer unit via a remote controller unit. 
     Preferably said transducer unit includes means for manual entry of instructions and a timer means both operationally associated with said mode switch whereby on switching said mode switch to the LOCAL mode, a user must enter via said entry means a valid identification number recognised by said transducer unit within a predetermined period of time timed by said timer means in order for further user instructions to be acted upon by said transducer unit, and in the absence of the entry of a valid identification number within said time period said transducer unit automatically shuts down so as to be non responsive to user input instructions for a second period of time timed by said timer means. 
     Preferably said transducer unit includes an ARM switch functional when said transducer unit is in the LOCAL mode of operation which, when activated causes said electric field generating means to generate said electromagnetic field. 
     Preferably said transducer unit includes a FIRE switch functional when said transducer unit is in the LOCAL mode of operation and which when activated within a predetermined time period after activation of the ARM switch causes the transducer unit to transmit the FIRE code to the ARCH module. 
     Preferably said system further includes a stemming bar for stemming a hole in which said ARCH module and detonator can be deposited and wherein said transducer unit includes a coil for generating said electromagnetic field, said coil mounted on or in the stemming bar so that lines of magnetic flux pass through the stemming bar and link with the power circuit to transfer operational power to the ARCH module by electromagnetic induction. 
     Advantageously the stemming bar is reusable. 
     Preferably said system further includes a remote controller unit by which a user can communicate instructions to said transducer unit from a location remote from said transducer unit. 
     Preferably said remote controller unit includes means for the manual entry of instructions by which a user must enter a valid identification number within a predetermined time period in order for said remote controller to establish a radio communication link with said transducer unit. Although in an alternate embodiment the remote controller can be key-switch operated. 
     Preferably said remote controller unit includes processor means for generating a unique identification code word which is continuously transmitted until an acknowledgment signal is received from said transducer unit corresponding to said identification code word, and wherein in the absence of receipt of said acknowledge signal within a predetermined time period said remote controller unit enters a RESET mode in which a user must once again enter a valid identification number to reinitiate the establishment of the radio communication link with said transducer unit. Preferably said remote controller unit further includes an ARM switch which upon activation, when a radio communication link has been established with said transducer unit, causes the remote controller unit to transmit an ARM code to transducer unit upon which said transducer unit generates said electromagnetic field. However in an alternative embodiment the remote controller can be hard-wired to the transducer unit. 
     Preferably the ARM code is transmitted by said remote controller to said transducer unit is different to the ARM code sent by said transducer unit to said ARCH module. 
     Preferably said transducer unit sends an acknowledgment signal to said remote controller unit upon receipt of the ARM code and said transducer unit thereafter initiates its timer means to time a first period within which to receive a FIRE code from said remote controller unit, wherein the absence of receipt of said FIRE code within said first period said transducer unit automatically shuts down for a second period of time. 
     Preferably said remote control unit includes a FIRE switch, which, when activated causes the remote control unit to transmit a FIRE code to said transducer unit which in turn upon on verified receipt thereof retransmits the FIRE code to said ARCH module. 
     Preferably the FIRE code transmitted by the remote controller to transducer unit is different to the FIRE code retransmitted by the transducer unit to the ARCH module. 
     According to another aspect of the present invention there is provided a controlled electromagnetic induction detonation system for decoupled in-hole initiation of an detonatable material, said system including: 
     an automated radio charge (ARCH) module coupled to a detonatable material and deposited in a hole formed in a hard material, the ARCH module having no permanent on board power supply but including a power circuit for extracting by means of electromagnetic induction operational power from a remotely generated electromagnetic field, the power circuit providing operational power for the ARCH module and arranged to generate a detonation current deliverable to the detonatable material, and means for receiving and decoding radio transmitted control signals including a FIRE code, the verified receipt of which causes delivery of the detonation current to the detonatable material; 
     a stemming bar for stemming the hole in which the energetic material and ARCH module are deposited; and, 
     a transducer unit for radio transmitting said control signals, said transducer unit having a coil for generating the electromagnetic field, the coil mounted on or in the stemming bar to effect the transfer of operational power to the ARCH module by electromagnetic induction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 
     FIG. 1 is a schematic representation of one embodiment of the controlled electromagnetic induction detonation system for initiating an energetic substance; 
     FIG. 2 is a block diagram of a remote controller of the system; 
     FIG. 3 is a block diagram of a transducer unit of the system; 
     FIG. 4 is a block diagram of an automated radio charge module of the system; 
     FIGS. 5,  6  and  7  when joined end to end for a state diagram describing the operation of the remote controller shown in FIG. 2; 
     FIGS. 8,  9  and  10  when joined end to end form a state diagram for the operation of the transducer module shown in FIG. 3; and 
     FIG. 11 is a block diagram of a second embodiment of a transducer unit and remote controller. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     From FIG. 1 it can be seen that one embodiment of the controlled electromagnetic induction detonation system  10  includes the following separate but interacting components: a remote controller  12 , a transducer unit  14 ; a stemming bar  16 ; and, an automated radio charge (ARCH) module  18 , although as will be apparent not all of these components are necessary in every embodiment of the invention. 
     When the system  10  is used for in situ excavation or fragmenting a boulder  22  a hole  20  is first drilled into the boulder  22 . The ARCH module  18  together with a coupled detonator  24  is pushed to the bottom of the hole  20  by the stemming bar  16 . The ARCH module  18  is typically spaced from or otherwise not directly attached to the proximal end of the stemming bar by an air gap  26 . In this way the ARCH module  18  is physically decoupled from the stemming bar  16 . The stemming bar  16  is dimensioned so that an end  28  distant the ARCH module  18  extends from the hole  20 . Located about end  28  is the transducer unit  14  or at least a coil/antenna of the transducer unit  14 . 
     The remote controller  12  can be located anywhere within the radio range of the transducer unit  14 . In general terms, the remote controller  12  is operated to transmit instructions to the transducer unit  14  that in turn sends instruction and operating power to the ARCH module  18  from a location remote from the ARCH module  18  for the subsequent initiation of the detonator  24 . The instructions from the remote controller  12  are sent from a safe location distant the detonator  24 . The instructions sent include ARM and FIRE codes. The transducer module  14  upon receipt of the ARM codes operates to generate an electromagnetic field and to retransmit the ARM code typically in a different format say ARM- 1 , to the ARCH module  18 . Advantageously, the ARM- 1  code is impressed onto the electromagnetic field. The transducer unit  14  then waits to receive the FIRE code from the remote controller  12 . If the FIRE code is received within a predetermined time period it is retransmitted in a different format, say FIRE- 1 , to the ARCH module  18  by being impressed on the induced electromagnetic field. 
     The ARCH module  18  does not have an onboard, nor is hard wired to a permanent power supply. Rather, as will be explained in great detail below, the ARCH module  18  includes circuits for extracting its operational power from the electromagnetic field generated remotely by the transducer unit  14 . Additionally, the ARCH module  18  upon receipt and internal verification and checking of the ARM- 1  and FIRE- 1  codes from the transducer module  14  can then produce and deliver an electric detonation current to the detonator  24 . 
     Referring to FIG. 2, the remote controller  12  is provided with a keypad and interface unit  30  by which information and instructions can be input. Signals can be transferred between the keypad and interface unit  30  to a micro controller  32  via a communication bus  34 . The micro controller in turn can communication with a FSK transceiver and antenna  36  via communication bus  38 . Electrical power from a rechargeable battery  40  is input to a power supply circuit  42  which delivers operating electrical power to the keypad  30 , micro controller  32  and FSK transceiver  36  via power rail  44 . 
     The hardware components of the controller  12  namely, the keypad  30 , micro controller  32 , FSK transceiver and antenna  36  and power supply circuit  42  are either standard off-the-shelf components or constructed in accordance with normal hardware design practice. In this regard, the micro controller  32  includes a micro processor with both a RAM and ROM and an address decoder etc. The specific functionality of the remote controller  12  is derived from its dedicated software. 
     The modus operandi of the remote controller  12  is depicted in the state diagrams of FIGS. 5,  6  and  7 . Specifically, FIG. 5 illustrates the POWER-UP routine for the remote controller  12 . State  300  simply indicates the start of the POWER-UP routine. State  302  indicates that the power to the remote controller  12  is turned on. This typically would occur on the flicking of a ON/OFF switch (not shown). After the power on state  302 , the micro controller  32  is booted at state  304 . Next, in state  306  a LED functionality check is performed. This step involves sequencing through a subroutine  308  to check that the LED indicators for the status of various conditions or states are operational. The conditions and states tested are the power state  310  indicating that the remote controller  12  is powered; the LINK state  312  indicating that a radio communication link has been established between the remote controller  12  and the transducer module  14 ; the ARM state  314  indicating that an ARCH module  18  is armed; the FIRE state  316  indicating that the FIRE code has been sent by the remote controller  12  to the ARCH module  18  via the transducer module  14 ; a FAULT state  318  indicative of a fault in the system  10  and the READY state  320  indicative that the remote controller  12  is ready to receive commands via its keypad and interface unit  30 . 
     The next state entered in the POWER-UP routine is the loop back FSK state  322 . When in this state, the remote controller  12  causes its FSK transceiver  36  to generate a test message at step  324  which is sent back to itself and checked to ensure correct coding and decoding of the FSK signals sent and by the remote controller  12 . If this tests detects no fault, the remote controller  12  enters the READY state  326  which is accompanied by the illumination of a READY LED on the remote controller. At this state, the remote controller  12  is simply waiting for the next instruction via the keypad and interface unit  30 . 
     Referring to FIG. 6, the remote controller next enters an ESTABLISH LINK routine upon activation of a LINK key on the keypad  30 , indicated as state  328 . The purpose of the ESTABLISH LINK routine is to establish a link, ie radio communication, with the transducer module  14 . The pressing of the LINK key on the keypad  30 , is detected and acted upon by subroutine  330  which instructs the controller  32  at step  332  to scan the keyboard  30 - and at step  334  to read the pressed key. Assuming that the key is the LINK key a corresponding LINK code is fetched from the memory section of micro controller  32  at state  336 , and then used to modulate an oscillator to produce a FSK signal which is communicated by bus  38  to the transceiver  36 . 
     The transceiver  36  is turned ON as indicated at state  338  and the LINK code sent at step  340 , by the transmitter  36  to the transceiver module  14 . Assuming that the LINK code is received by the transducer module  14 , and is correctly decoded, the transducer module  14  transmits an acknowledgment back, (ACK BACK) code to the remote controller  12  as indicated at step  342 . The ACK BACK code is then processed at step  344  and various test messages generated in state  344  indicative of the LINK test results. Assuming that the link between the remote controller  12  and transceiver module  14  is functioning to a predetermined reliability, a radio link will be established as indicated at state  348 . 
     Once the radio link is established, the remote controller  12  at routine  350  scans the keyboard  30  for depression of the ARM key, and at step  352  starts a timer. The timer counts a period set in step  354 , which can be adjusted but is shown as a nominal 10 second period. The remote controller  12  remains in the scan state  350  unit the expiration of the period set in state  354 . If the ARM key is not activated within this period the radio link to the transducer unit  14  is disconnected and lock out timer is initiated at state  356  which prohibits the reestablishment of the radio link with the transducer module  14  for a predetermined period of time for example five minutes. If, during the period in state  354 , the ARM key is pressed an ARM routine shown in FIG. 7 is entered. 
     The pressing/activation of the ARM key is shown as state  358 . The depressing of the ARM key is detected by the micro controller  12  scanning the keypad at state  360 , reading the key pressed at state  362 , and if the key is the ARM key, the micro controller  32  fetches an ARM code at state  364  from its memory. The code is converted to a FSK signal for transmission. At state  366  the micro controller  32  simply ensures that the transceiver  36  is ON and OK. Assuming this to be the case, the FSK signal containing the ARM code is transmitted at state  368  via the previously established LINK to the transducer module  14 . The remote controller  12  then waits at state  370  for confirmation of receipt of the ARM code from the transducer module  14 . Upon receipt of confirmation the remove controller  12  simultaneously initiates a FIRE timer at state  372  and arms the ARCH module  18  at state  374 . At state  374 , the FIRE timer counts down a nominal period, say five seconds within which the FIRE key on the keypad  30  must be depressed in order to fire (ie initiate) the detonator  24 . If this does not occur within the predetermined time period, then the remote controller  32  shuts itself down at state  374  and initiates the same lockout time at state  376  preventing operation of the remote controller  12  for a nominal five minute period. 
     During the period set by the FIRE timer the micro controller  32  enters a FIRE scanning state  378  in which it scans the keypad  30  for pressing of the FIRE key. This is similar to the ARM key state  358 , and involves the micro controller  12  scanning the key pad (state  360 ) reading the key pad (state  362 ) and getting a corresponding FIRE code (state  364 ) from its memory in the event that the activation of the FIRE key is detected. The FIRE code modulates an oscillator to produce a FSK signal for transmission. State  366  is then reentered, the transceiver  36  OKed and at state  368  the FSK signal containing the FIRE code is transmitted to the transducer module  14 . 
     FIG. 3 illustrates in block diagram form the configuration of a transducer module  14 . The transducer module  14  includes a FSK transceiver  46  which communicates with a micro controller  48  via bus  50 . Micro controller  48  also communicates with a chopper  52  via bus  54 . A rechargeable battery  56  is included within the transceiver module  14  as its power source. The battery  56  is in electrical connection with a DC power supply circuit  58  which delivers power to the transceiver  46 , micro controller  48 , and chopper  52  via power rail  60 . Also included within the transducer module  14  is a coil  62  for producing an electromagnetic field. Both the micro controller  48  and chopper  52  are inductively coupled to the coil  62  via respective inductive couplings  64  and  66 . 
     In general terms, the transducer module  14  initiates the generation of specific frequency oscillations generated internally upon the receipt of encoded command signals from the remote controller  12 . When certain commands are received and confirmed by its own transceiver  46  the micro controller  48  turns ON an oscillator and superimposes a series of digital code word instructions encoded as unique frequency shift keying (FSK) onto the oscillator. The micro controller  48  has several functions including: 
     Establishing a communications link with the remote controller. 
     Enabling the chopper  52  when it receives an ARM code or instruction from the remote controller  12 . This provides operating power to the ARCH module  18  then sends control words to the ARCH module  18  after allowing time for power stabilisation. 
     Monitors the duration that the chopper  52  is turned ON and after a nominal period of 10 seconds switches the chopper  52  OFF, and sends a signal back to the remote controller  12  that the transducer module  14  is timed out. This prohibits a retry or reentry of further instructions for a programmable time period which normally would be in the order of five minutes. 
     Sends FIRE code to the ARCH module  18 , and then shuts down the chopper  52 . 
     The transducer module regenerates its own control and initiation words once it receives the primary instructions from the remote controller  12 . On receipt of the ARM code from the remote controller  12 , the transducer module  14  will generate its own corresponding ARM- 1  code. The same regeneration principle applies to the receipt of the FIRE code from the remote controller  12 , with the regeneration of a FIRE- 1  code. The operation of the transducer module is shown diagraphically in FIGS. 8-10. 
     FIG. 8 illustrates the POWER-UP routine for the transducer module  14 . The transducer module  14  has an internal power source, namely the battery  56  and therefore is initially in a power on state  400 . Subsequent to the power on state  400 , the micro controller  48  is booted at state  402 . At state  404  a functionality test is conducted on the chopper  52 . The status of the transducer module  14  is determined and a status byte is stored at state  406 . The stored status byte is later sent back to the remote controller upon establishment of the communications link therewith so that the remote controller  12  can check the status of the transducer module  14 . 
     Upon completion of the POWER-UP routine, the transducer module  14  enters a listening state  408  in which it awaits receipt of the LINK code from the remote controller  12 . If receipt of the LINK code is detected at state  410 , the transducer module  14  gets an appropriate response code from the memory of the micro controller  48  at state  412  and generates an acknowledgment back signal at state  414 . Simultaneously, the transmitter portion to the transceiver  46  is turned ON at state  416  so that the acknowledgment back signal generated state  414  can be sent at state  418  back to the remote controller  12 . It is this acknowledgment signal which is acted upon at states  342 ,  344 ,  346  and  348  in the ESTABLISH LINK routine of the remote controller  12 . A link watchdog  420  also operates to ensure maintenance of the link between the remote controller  12  and transducer module  14 . This is effected by watching at state  422  for the issuance of the acknowledgment signal from state  418  within a nominal predetermined time period such as five seconds. If no acknowledgment signal is sent at state  418  within five seconds of receipt of the LINK code at state  408  the transceiver  46  is turned OFF at state  424  effectively closing down the ESTABLISH LINK subroutine and resetting the state of the transducer module  14  to POWER ON state  400 . 
     Assuming that the acknowledgment signal is received within the time period set at state  422 , the transducer module  14  enters state  426  at which it listens for the ARM code or command from the remote controller  12 . This commences the ARM routine shown in FIG.  10 . At state  428  the micro controller  48  interrogates signals received by the transceiver  46  to ascertain whether or not it contains the ARM code. This is achieved by decoding the FSK signals transmitted by the remote controller  12  and comparing the decoded signals with predetermined signals stored in a look up table in the memory of the micro controller  48 . If the ARM code is received and verified the micro controller  48  turns ON the chopper  52  at state  438 . The chopper  52  is of conventional construction and operates in the standard manner to produce an AC output from the DC power supply  58 . This output is coupled by the inductive coupling  66  to the coil  62 . In one embodiment, the coil  62  is wound around the end  28  of the stemming bar  16 . Therefore, at the stemming bar  16  together with the coil  62 , act as an electromagnet when the chopper  52  is operating. Corresponding lines of magnetic flux are substantially confined to the stemming bar  16 , and as will be described in greater detail below, traverse the gap  26  and link with a pick up coil in the ARCH module  18  to induce an electrical current which provides power for the ARCH modules  18 . However it is preferred that the coil  62  is actually mounted inside the stemming bar  16  at an end nearest the detonator  24  when the stemming bar  16  is in the hole  20 . This will minimise energy loss and maximise the inductive coupling and energy transfer to the ARCH module  18 . In this variation lead wires pass through the stemming bar and connect the coil  62  to the remainder of the transducer unit  14 . 
     Since the ARCH module  18  does not have its own on board permanent power supply, the transducer module  14  next enters a timer state  432  in which it allows sufficient time for power levels to be stabilised within the ARCH module  18 . As a safely feature typically the remotely generated electromagnetic field would not carry sufficient instantaneous power to initiate the detonator  24 . Therefore the ARCH module  18  would include electrical storage and integration circuits to accumulate over time the required power to operate the ARCH module and generate the necessary initiation current. After stabilisation, the transducer module  14  sends a FSK training signal at state  434  to the ARCH module  18 . 
     The ARM- 1  code is fetched from the memory of the micro controller  48  at state  436 . The ARM- 1  code is then used modulate an oscillator to produce an FSK signal which, at state  438  is output from the micro controller  48  and coupled to the coil  62  via inductive coupling  64 , and thus transmitted to the ARCH module  18 . That is, the lines of magnetic flux created by the current flowing through coil  62  provide not only operating power to the ARCH module  18  but also contain control signals including the arming code ARM- 1  and firing code FIRE- 1 . 
     An acknowledgment signal is then sent back at state  440  to the remote controller  12  acknowledging receipt of the ARM code and the transmission of the ARM- 1  code. This acknowledgment signal is waited for at state  370  in the ARM routine for the remote controller  12  shown in FIG.  7 . Upon issuing of the acknowledgment signal the transducer module  14  initiates a FIRE timer at state  442 , and at state  444  counts a predetermined shut down period, for example five seconds, within which to receive the FIRE code from the remote controller  12 . If the FIRE code is not received within the predetermined time at state  444  the transducer module  14  shuts down. This of course turns OFF the chopper  52  thus cutting off power to the ARCH module  18 . 
     If the FIRE code is received from the remote controller  12  within the predetermined period, the micro controller  48  fetches a FIRE- 1  code from its memory which is different to the FIRE code sent by remote controller  12 , uses that code to modulate an oscillator and produce an FSK signal which is coupled by inductive coupling  64  to the coil  62  and transmitted to the ARCH module  18 . 
     Referring to FIG. 4, the ARCH module  18  comprises a pick up coil  68  which is positioned to link with the lines of magnetic flux passing through the stemming bar  16 . The coil  68  also includes inductive output couplings  70  and  72 . The output from coupling  70  is feed to a power supply  74  for powering the module  18  while the coupling  72  is input to an FSK receiver  76 . The power supply  74  detects the induced electromagnetic field, and rectifies, integrates and uses the resulting DC voltage to charge an RC combination. The storage capacity of the onboard capacitor in the combination is sufficient to provide the working voltage and power requirements for the other onboard electronics as well as to provide the detonating current and voltage that is required to ignite detonator  24 . 
     The FSK receiver  76  detects FSK signals that are being transmitted by the transceiver  46  of transducer module  14 . As previously described, these FSK signals are superimposed on the induced electromagnetic field and magnetic flux lines. The input levels presented to the FSK receiver  76  may vary therefore it is desirable that this device includes an internal automatic level control (ALC). This ensures a constant signal level is presented to the receiver  76 . As the FSK receiver  76  is powered by the onboard power supply it is desirable that this consume an absolute minimum of power and operate at as low a voltage as possible. FSK receiver produces a digital output which is coupled directly to a onboard micro controller  78 . The micro controller  78  functions to monitor the digital word stream from the FSK receiver and look for appropriate commands words that it would expect to see from the remote controller (as regenerated and retransmitted by the transducer module  14 ). 
     The power supply  74  provides the micro controller  78  with a stabilised voltage supply thereby ensuring that it is not subject to the rise of the power supply as the voltage is induced in coil  68 . On “power up” the micro controller  78  undertakes a series of status and housekeeping checks before allowing itself to listen for incoming instructions. The nature of these inhouse checks confirm that correct working volts are available and also the status and condition of its input and output control lines. 
     Once the micro controller  78  has been satisfied that it is operating correctly it then commences to listen out for control words transmitted from the remote controller  12  via the transducer module  14 . In the overall timing of the system  10  once the transducer module  14  has produced the electromagnetic field via chopper  52 , coil  62  and the stemming bar  16 , the subsequent ARM- 1  and FIRE- 1  codes must be received within predetermined times frames as described above. If this does not occur the micro controller  78  will ignore all incoming signals and effectively go to sleep. The only way that the sequence can be reinitialised after this has occurred is to be powered down and repowered. This can be done by resetting the remote controller  12  and repeating the firing sequence. 
     When the transducer module  14  receives an ARM code from the remote controller  12  it energises its coil  62 , waits for a period of time that corresponds with the settling time required by the ARCH power supply and inhouse ARCH micro checks (state  432 ), then sends its own internally generated ARM- 1  code to the ARCH module  18 . If the transducer module  14  does not receive the FIRE code from the remote controller  12  within a nominal time period after receiving the ARM code, then it will switch OFF the chopper  52  thereby removing power to the ARCH module  18 . This proceeding sequence will result in the ARCH module  18  expecting to receive a FIRE- 1  code from the transducer module  14  within a nominal five second window. If this does not occur then it is assumed that the transducer module  14  has not received the FIRE code from the remote controller  12  and therefore the micro controller  78  will shut down the ARCH module  18  and revert to a SLEEP mode. 
     When the micro controller  18  receives and decodes the FIRE- 1  code from the transducer module  14 , it initiates the detonation sequence. This is achieved by signally one or more of its output control lines  82  to a certain output state in turn allowing a logic array  84  to be triggered resulting in the energising of a firing switch or relay  86  that is connected to the detonator  24 . The relay  86  is preferably a DPDT relay, with one set of contacts providing a permanent short circuit across leads  88  to the detonator  24 . This ensures that no current can flow to the detonator  24  until the short circuit is removed by actuating the relay  86 . This can only be down once the micro controller  78  processes the FIRE- 1  command, and all other logic parameters and conditions have been satisfied. Typically this may involve the transmission of the FIRE- 1  code by the transducer module  14  a predetermined number of times (say 30 times) and the correct decoding and checking of that signal by the receiver  76  and micro controller  78  on every instance. 
     When FIRE- 1  code is received and all internal checks have been satisfied a detonating current is switched to the detonator leads  88  via the power supply  74  initiating or detonating the detonator  24 . 
     A second embodiment of the radio detonation system  10  is shown in FIG.  11 . In the second embodiment, the ARCH module  18  is unchanged and therefore not shown in FIG.  11 . The differences between the first and second embodiments lies in the configuration and operation of the remote control unit  12 ′ and the transducer unit  14 ′. The essential difference which will be explained in great detail below, is that the transducer unit  14 ′ can be placed in a LOCAL mode of operation allowing a user to manually enter various instructions and codes for transmission to the ARCH module. This therefore allows the user to set off the detonator  24  from say behind a piece of machinery or barrier via direct use of the transducer unit  14 ′ instead of having to physically move a substantial distance away from the detonator  24  and use the remote controller to set off the charge  24 . When the transducer unit  14 ′ is in the REMOTE mode of operation then the remote control unit  12 ′ can be used in essentially the same manner as remote controller  12  described herein above to set off the detonator  24 . 
     When the transducer unit  14 ′ is initially turned ON it automatically enters the REMOTE mode of operation and a REMOTE indicator  500  will illuminate. Watch keeping power is provided to microcontroller  502  and fail safe code generators. ARM and FIRE switches  506  and  508  respectively will have no effect until a user enters a valid personal identification number (PIN) via manual entry means such as a keypad  510  and mode switch  512  is switched to toggle the transducer unit  14 ′ to the LOCAL mode. The main loop of the microcontroller  502  now enters a WAIT state and monitors for incoming commands and signals from the remote controller  12 ′ and scans its keypad  510  and switches  506 ,  508  and  512 . 
     It is possible to select the LOCAL mode of operation by switching the mode switch  512 . Once this is done a number of events must occur and fail safe logic must be satisfied before the LOCAL mode is actually entered. Firstly, the REMOTE indicator  500  will remain illuminated, even though the MODE switch  512  has been switched to the LOCAL mode position. A LOCAL mode indicator  514  will illuminate after the authentication process has been successfully completed. 
     Once the mode switch  512  is activated, a time in a timer and logic system  516  will count down a predetermined period such as 10 seconds. Within this time, a user must enter a valid PIN via the keypad  510 . 
     If a user enters a valid PIN number on the keypad  510  within a time limit counted by the timer unit  516  the REMOTE indicator  500  is extinguished and the LOCAL indicator  514  is illuminated. Also, an A 1 S generator  518  within the transducer unit  14 ′ is activated. The A 1 S generator  518  generates an all  1 &#39;s code or tone that is transmitted by the transceiver  504  to the remote controller unit  12 ′. The remote controller unit  12 ′ is configured to ensure that it cannot be accessed or operated while it receives the all  1 &#39;s tone from the transducer unit  14 ′. 
     In the event that an invalid PIN is entered by the keyboard  510  or no PIN is entered was not entered within the preset time period the microcontroller  502  is shut down for a second predetermined time period before which a user can again attempt to operate the transducer unit  14 ′. Valid PIN&#39;s can be stored in the microcontroller  502 . It is envisaged that these PIN&#39;s can be changed or deleted at will. 
     When the transducer unit  14 ′ is switched to the LOCAL mode and the ARM switch  506  is pushed or otherwise activated a DC voltage either onboard or controlled by the transducer unit  14 ′ is switched to an inverter (ie chopper) to produce an AC voltage output that is routed via a stemming bar isolation switch (not shown) to a stemming bar coil (not shown but equivalent to coil  62  in FIG. 3) forming part of the transceiver  504 . This generates the electromagnetic field for inducing operational power for the ARCH module  18 . The transducer unit  14 ′ and stemming bar coil are separate components connected by wires. In this way the coil can be placed about the stemming bar  20  and the transducer unit  14 ′ operated from behind a piece of machinery or recoil device placed against the stemming bar  20 . As with the previous embodiment, the ARM condition is held for a predetermined period of time that can be adjusted between 0 and 9 seconds. If the FIRE switch  508  is not activated or depressed within that period of time the transducer unit  14 ′ disconnects power to the inverter (thereby starving the ARCH module at power) and shuts itself down for a predetermined period of time. If the FIRE switch  508  is activated within the provide time frame, the microcontroller  502  firstly validates or verifies the activation of the FIRE switch  508  and then generates a FIRE code in the form of a 128 bit datastream. This datastream is used to effectively modulate the output of the inverter causing it to operate as a pulse width modulation (PWM) source for the transceiver  504 . The resulting PWM AC voltage provides both the power and signalling format required by the ARCH module  18 . 
     The remote controller  12 ′ can only be operated when the transducer unit  14 ′ has been switched to the REMOTE mode of operation. If the transducer unit  14 ′ is in the LOCAL operating mode an indicator lamp on the remote controller unit  12 ′ will be illuminated and any switches, keypads or other input means on the remote controller unit  12 ′ will be effectively disabled thereby denying the user to enter any commands into the remote control unit  12 ′. When power is first turned ON in the remote controller unit  12 ′ watch keeping power is applied to its onboard microcontroller  520  as well as its transceiver  522  and A 1 S decoder  524 . ARM and FIRE switches  526  and  528  respectively will have no effect until a LOCAL mode of operation of the remote control unit  12 ′ has been established. Remote controller unit  12 ′ includes a REMOTE mode indicator  530  and LOCAL mode indicator  532 . 
     When the remote control unit  12 ′ is turned ON and only when the transducer unit  14 ′ has been switched to the REMOTE mode of operation, the LOCAL mode indicator  532  illuminates and the REMOTE mode indicator  530  extinguishes. The LOCAL mode indicator  532  will only illuminate after an authentication process has been successfully completed. 
     When the mode selector switch  512  on a transducer unit  14 ′ is switched to REMOTE mode, 1.5 kHz tone (ie all  1 &#39;s code) is generated via the A 1 S encoder  518  and transmitted by the transceiver  504 . The transceiver  522  of the remote control unit  12 ′ must receive and decode this tone before it can switch to the LOCAL operating mode. This is a fail safe system so that if the remote controller  12 ′ is out of range of if the transducer unit  14 ′ is in the LOCAL operating mode then it cannot be accessed. 
     Assuming all is in order and that the A 1 S decoder  524  decodes a valid tone, the A 1 S decoder  524  then initiates a timer in a logic and timer unit  526  to initiate the counting of a first time period normally of say 10 seconds. During this 10 second period an operator must enter a valid PIN via a keypad  534 . If a PIN is not detected in this predetermined period of time or the PIN is not valid the microcontroller  520  will shut down for a second predetermined period of time before which it can be reactivated. 
     If a valid PIN has been entered and validated then the microcontroller  520  operates to establish a radio communication link with the transducer unit  14 ′ in a similar manner as described in relation to the first embodiment. In broad general terms, the microcontroller  520  generates a unique identification code word (ie LINK code) and continuously sends the code word via its transceiver  522  until an acknowledgment is received from the transducer unit  14 ′. If no acknowledgment has been received after a set (but adjustable) period of time (say 60 seconds) then the microcontroller  520  enters a reset mode and the operator will again be prompted for a valid PIN. The main loop program for the microcontroller  520  is structured such that it will ignore any activity on its ARM/FIRE switches  526 ,  528  until such time as a radio communication link to the transducer unit  14 ′ has been established. In the event that a radio communication link is established and an operator then pushes the ARM switch  526  an ARM code is sent via the transceiver  522  to the transducer unit  14 ′. The transducer  14 ′ then executes its arming sequence however the transducer unit  14 ′ must acknowledge receipt of the ARM code before the microcontroller  520  is enabled to proceed further. On receipt of valid acknowledgment from the transducer unit  14 ′, a timer within the unit  526  is again operated to countdown a predetermined time adjustable between 0 and 9 seconds. In addition an ARMED indicator (not shown) is illuminated on the remote controller  12 ′. If the FIRE switch  528  is activated within the aforementioned time period, the microcontroller  520  will send a FIRE code via transceiver  522  to the transducer unit  14 ′. The FIRE code from the remote control unit  12 ′ may typically be a 32 bit word. The transducer unit  14 ′ must acknowledge receipt of the FIRE code from the transducer unit  12 ′ and receive the same code a second time before the transducer unit  14 ′ enters its firing cycle. 
     From the foregoing description it would be apparent that the system  10  can be used to initiate an electric detonator or electric match to enable detonation or rapid decomposition of an energetic material including an explosive or propellent-type material to occur within a previously drilled hole in a rock face or similar material requiring blasting or fragmentation. It is envisaged that a major application for the ARCH module  18  which has the potential to revolutionise hard rock drilling methods is in situ mining. In this regard, a custom designed machine can be made that can drill a hole or holes in a rock formation and automatically insert a ARCH module  18  and stemming bar  16  with transducer  14  or at least the transducer coil. The stemming bar can be reused (as of course can the transducer  14  and remote controller  12 ), the ARCH module  18  is however destroyed. Thus the machine would carry a supply of ARCH modules with attached detonators  24  for depositing into holes together with energetic material. More particularly, it is envisaged that the machine in question would typically have a boom that can be rotated about its longitudinal axis, with the boom supporting a drill for drilling holes in a rock formation; a delivery system for delivering or depositing an ARCH module  18  with attached detonator  24  and a charge of energetic material into the drilled hole; and, a ram for inserting and subsequently retracting the stemming bar  16  from the hole. The machine could be operated in essentially a continuous manner so that firstly a hole is drilled, the boom then rotated to align the delivery means with the hole to deposit an ARCH module  18  and detonator  24  into the hole; and then the boom rotated again so the ram can insert the stemming bar  16 . An operator of a machine can then from the machine cabin or from behind the machine operate the transducer module  14 ′(being in its LOCAL mode of operation) to remotely set off the detonator  24 . This process is then sequentially repeated. 
     It is further envisaged that the ARCH module  18  and system  10  can be used in non mining applications such as civil excavation works and for initiating fireworks etc. 
     A substantial benefit of the ARCH module  18  over the prior art is that there is no need to have any leads or initiating cord physically in the hole in which the detonator is located in order to initiate detonation. Such leads can act as antennas to receive stray electromagnetic fields causing the induction of currents which may prematurely initiate detonation. Also physically placing leads or cords into a blast hole is inherently dangerous due to the possibility of rock falls. As a result of this alone, the safety aspect of the ARCH module  18  is substantially greater than that in comparison to previously known devices and systems for setting off detonators. In addition the ARCH module has in built intelligence so as to not provide or deliver a detonation current even if power is induced by a stray electromagnetic field, since it must also receive and verify a valid FIRE code. 
     Operating safety is further enhanced by the fact that a short circuit is applied across the detonator of the ARCH module  18  until such a time as the FIRE code is received and verified. This makes it impossible for a detonating current to pass to the detonator. 
     Now that an embodiment of the present invention has been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. For example, the frequency shift keying and pulse width modulation are used as the modulation regimes for the system  10  in the described embodiments. However other modulation schemes can be used such as coherent or noncoherent amplitude shift keying (ASK) or phase shift keying (PSK) or differentially coherent phase shift keying (DPSK). Also, different acknowledgment protocols can be used between various components of the system  10  for acknowledging receipt of various control signals and codes. Further, the predetermined time limits mentioned above, for example at states  354 ,  374  and  422  can be altered. It is also envisaged that it would be possible to supply power and control signals/codes to the ARCH module  18  via separate signals or fields rather than combining them on a single signal. Further, the communication and power transfer between the remote controller  12  and transducer  14 ′ can be via cables or wires, rather than by radio communication. However it is important that communication between the transducer  14  and ARCH module  18  is by virtue of electromagnetic waves rather than by hard wiring. 
     All such modifications and variations are deemed to be within the scope of the present invention the nature of which is to be determined from the foregoing description and the appended claims.