WO2006108416A1

WO2006108416A1 - Maritime radio communications device

Info

Publication number: WO2006108416A1
Application number: PCT/DK2006/000196
Authority: WO
Inventors: Henrik Fyhn; Henrik Kalstrup
Original assignee: Thrane & Thrane A/S
Priority date: 2005-04-11
Filing date: 2006-04-06
Publication date: 2006-10-19

Abstract

A maritime radio communications device comprising a radio receiver for receiving voice messages via at least one predetermined radio frequency communications channel; a recording buffer for recording a plurality of said received voice messages; and a user-controllable replay means for replaying a user-selected one of said recorded voice messages.

Description

Maritime radio communications device

The invention relates to a maritime radio communications device and, in particular, a maritime radio communications device comprising a radio receiver for receiving voice messages via a radio-frequency communications signal.

Maritime radio communications devices are widely used on maritime vessels as a means for voice communication between vessels. Typically, such devices operate in one or more radio frequency band, e.g. the very high frequency (VHF) band.

Such communications devices allow operators on different vessels to communicate with each other, e.g. in order to warn each other about dangerous situations, to agree on some actions as to prevent a dangerous situation, or the like. Hence, two vessel operators may exchange important information, e.g. information about a change in course as to avoid a collision, information about a channel number or a frequency of a new communications channel to which one operator wishes the other operator to switch.

Consequently, a proper reception of the voice message can be imperative for the safety of the vessel(s).

However, the received voice messages by one such device may be difficult for the operator to understand, e.g. because the reception conditions are inferior, because the sending party speaks unclear, e.g. during a stress situation or due to language problems, because there is surrounding noise on the receiving vessel, e.g. from machines, other communications equipment, or the like. Furthermore, the operator on the receiving vessel may misunderstand or miss a message, because the operator may not be in the vicinity of the communications device, or be preoccupied with other tasks, or in a stressed situation, or the like.

The above and other problems are solved when a maritime communications device further comprises a recording buffer for recording a plurality of said received voice messages; and a user-controllable replay means for replaying a user-selected one of said recorded voice messages. Consequently, the device provides functionality for repeating an incoming voice message in case the operator did not understand the message in the first instance.

In embodiments of the invention, the replay function performs automatic and continual recordings of all received voice messages - or at least all voice messages received with a sufficient quality - by buffering the received audio signal without user interaction. In particular, in embodiments of the invention, the replay function records all received voice messages while they are reproduced over a loudspeaker, earpiece or other audio output device. The received audio can be recalled/replayed by pushing a single replay button until the desired rewind time is achieved - up to the maximum length of the recording buffer.

In one embodiment, the recording buffer has a predetermined storage capacity corresponding to a predetermined total recording time; and wherein the recording buffer is controlled to record all received voice messages such that the most recently received voice messages up to said total recording time are stored, e.g. as a finite or circular buffer. It has been realised that in most situations where an operator does not understand a received message, only the most recent messages need to be replayed, while older messages can be discarded/overwritten. Hence, an efficient storage mechanism is provided that allows storage of the most recent messages without requiring a large storage capacity. Furthermore, a limited size of the buffer makes it easier for the operator to find the right voice message again. It has turned out that a recording time between 30 seconds and 5 minutes is useful, in particular a recording time between 1 minute and 2 minutes, e.g. about 90 seconds. However larger or smaller buffers may be used as well.

In one embodiment, the radio receiver comprises a receiver circuit for receiving a radio-frequency signal and to generate an audio signal from said received radio-frequency signal; and a squelch circuit adapted to control the recording buffer to record said audio signal as a received voice message only when the received radio-signal fulfils a predetermined condition, e.g. when signal level of the received radio-frequency signal is above a pre-selected threshold level or when the noise level of the received signal is below a predetermined threshold. Squelch circuits, i.e. circuits that mute the audio output of a receiver when the received signal is too weak to provide acceptable audio are known as such, and they may employ different techniques and/or criteria, including but not limited to noise squelch, signal level squelch, tone coded squelch. Alternatively or additionally, the squelch function may include a voice activity detector. Consequently, the recording buffer is not filled up by noise rather than actual voice messages, thereby facilitating a quick retrieval of an important voice message. Furthermore, the selective recording reduces the risk that an important voice message is overwritten by a more recent message before it can be replayed. Hence, a reliable replay function is achieved even for a small buffer size.

In one embodiment, the maritime communications device further comprises a message database for storing a number of message information data items, each message information data item comprising information about one of the recorded voice messages, such as a channel number and/or frequency of a communications channel over which the voice message was received and/or a date and/or time of recording and/or a message duration and/or a current geographic position, e.g. from a GPS receiver. Consequently, the stored information allows a particular simple retrieval of a relevant message, and provides important additional information such as the channel number / frequency and time of receipt.

The recording buffer may be any suitable circuit or storage device for storing audio signals in analogue or digital form. Examples of a recording buffer include a memory for digital storage of audio signals, such as a volatile or non-volatile memory, such as a random access memory (RAM), a flash memory, a hard disk, or the like. The recording buffer and the message database may be physically separate memories or other storage means, or they may be separate sections of a single storage means. In yet another alternative embodiment, the message data items may be stored interleaved with the voice recordings of the recording buffer.

In one embodiment, the maritime communications device further comprises processing means adapted to generate a message information data item for each recorded voice message, said message information data item being indicative of the position of the recorded voice message in the recording buffer. Hence, the message information data items allow the device to determine the position of the recorded message on the tape. For example, the message information data item may include information about the absolute location in the buffer or the relative location in the buffer, e.g. relative to the previous message, in form of a message duration, and/or the like.

In one embodiment, the message information data item comprises information about a duration of the voice message; wherein the processing means is adapted to receive trigger signals from the squelch circuit indicative of a start and stop of the recording, and to calculate the duration from said trigger signals, thereby providing a relation between the stored data items and an actual position of the recorded message in the recording buffer. The term processing means is intended to include any suitably programmed general-purpose microprocessor, a special-purpose circuit or device, or a combination thereof. Examples of such circuits include an application-specific integrated circuit (ASIC), a digital signal processing (DSP) circuit, and the like.

In one embodiment, the maritime communications device further comprises a user-operatable activation means adapted to control the replay means; wherein the user-operatable activation means is adapted to receive a user- input indicative of a position in the recording buffer, and wherein the replay means is adapted to selectively replay one or more recorded voice messages responsive to the user-input. Consequently, an easy-to-use user interface is provided for a fast and selective retrieval of recorded messages. The activation means may be a push button or any other suitable input device, e.g. a button implemented as a part of a graphical user-interface that is operatable by a pointing device, navigation keys, a touch screen, or the like.

In one embodiment, the replay means is adapted to retrieve a message information data item from the database based on the user-input, and the maritime radio communications device comprises a display for displaying the retrieved message information data item. Hence, during replay the stored message information is displayed, thereby further providing important information to the operator. Furthermore, the displayed message information, e.g. time of receipt and communications channel/frequency, helps the operator to ensure that the replayed message actually is the desired message.

In particular, in one embodiment, the activation means is adapted to detect a duration of an activation of said activation means by the user - e.g. the time a push button is pressed - and wherein the replay means is adapted to selectively replay one or more recorded voice messages responsive to the detected duration of the activation. For example, the duration of activation may be translated into a rewind time within the recording buffer. Consequently, a particular intuitive single-action user interface is provided. In alternative embodiments, the replay function may be operated by more than one activation means or a dual-function activation means, e.g. a knob for setting the rewind time and a push button for initiating the replay. In yet another embodiment, the replay function may be activated by a push button that allows the rewind time to be increased in discrete increments, e.g. by repeated activation of the button, wherein each activation increases the rewind time by a fixed interval, e.g. 10 sec, or where each activation causes the buffer to rewind by an amount corresponding to the duration of the preceding message in the message database.

In some embodiments, the communications device comprises a multi- channel mode or a scanning mode, where a plurality of channels or frequencies are regularly, e.g. successively or periodically, scanned for activity. When the squelch circuit detects an incoming message on one of the channels/frequencies during the scan, the scan is interrupted so that the message may be received and recorded in the recording buffer. In some embodiments, the scanning is restarted when the squelch closes again. Alternatively or additionally, the scanning may be restarted after a predetermined time. Hence, in such a scanning mode all incoming messages on any of the channels are recorded in the recording buffer, and the corresponding channel numbers or frequencies as well as the date and time of receipt are stored in the message database. Hence, when the operator is temporarily unable to listen to the received messages, he/she may replay the most recent messages upon return.

In the following, embodiments of the invention will be described in greater detail and with reference to the drawings in which: Fig. 1 shows an overall block diagram of a maritime communications device.

Fig. 2 shows an example of a user interface on a front panel of a maritime communications device.

Fig. 3 shows a more detailed functional block diagram of replay function.

It is understood that different functions illustrated as distinct blocks in a block diagram, may be implemented by physically separate circuits or devices, or they may be implemented by a smaller number of devices/units, e.g. by a suitably programmed microprocessor, a DSP circuit, an ASIC, or the like.

Fig. 1 shows an overall block diagram of a maritime communications device, e.g. for instalment on a maritime vessel. The maritime communications device, generally designated 101 comprises an antenna 102 for receiving/transmitting radio-frequency, e.g. VHF, signals, a transmitter circuit 103, and a receiver circuit 104. The receiver circuit receives the received signal from the antenna and generates a corresponding audio signal 105. The transmitter circuit 103 receives an outgoing audio signal 106 and feeds a corresponding RF signal to the antenna. Such receiver/transmitter circuits are known as such in the art, and they perform various signal processing functions, including one or more of the following: amplification, filtering, modulation/demodulation, etc.

The received audio signal 105 is fed to a signal processing and control circuit 107 and from there to a loudspeaker 108 that reproduces the received voice messages. The processing and control circuit 107 stores the received messages and controls the replay function described herein. The signal processing and control circuit further controls the operation of the communications device, including functions such as channel or frequency selection, volume control, etc. The communications device further comprises a microphone 109, and the signal processing and control circuit 107 feeds audio signals received from the microphone as an outgoing audio signal to the transmitter circuit 103. The loudspeaker and/or the microphone may be integrated in the device or they may be an external microphone and/or loudspeaker/earpiece, e.g. in the form of a head set. The communications device further comprises a user interface 110 allowing an operator to control the functions of the device. An example of such a user interface on the front panel of a maritime radio communications device will now be described with reference to fig. 2

Fig. 2 shows an example of a user interface of a maritime communications device. The user interface comprises a combined push button / volume knob 14 for powering the device on/off and for selecting the volume, a replay button 15 for invoking the replay function described herein, a squelsh wheel button 13 for setting a threshold level for the squelsh function, an upper display 5 for displaying the current channel number or frequency, a graphic display 12, a squelsh level indicator 3, a volume level indicator 2, a number of indicator lamps 4, 6, a dim button 7, a MENU button 8, a mute button 9, a specific selector button for channel no. 16 used for distress and calling, an "OK" button 17, arrow keys 18, a keyboard 10, a distress button 11 , and a loudspeaker 1. The menu button 8, the OK button 17, and the arrow keys 18 allow a selection of communications channels/frequencies, and to perform various setup functions, e.g. display contrast, color, channel setup, selection of different operation modes, etc.

The replay facility built allows a copy of the last 90 seconds of received voice data to be replayed in the acoustic devices, e.g. the internal loudspeaker 1 or an external loudspeaker, headset, earpiece, or the like. Received voice data is defined as audio data which is qualified to pass the squelch circuit, e.g. in relation to a predetermined squelch level that defines how high an audio quality is required to pass the squelch. For example, the squelch level may correspond to a minimum signal level, a maximum noise level, or the like. The squelch level is set by turning the squelch knob 3. The actual squelch level is visualised by the squelch indicator bar 3.

If voice data is captured that exceeds the buffer length, i.e. in this embodiment after a 90 seconds sequence has been recorded, the oldest recorded voice data are overwritten. Hence, the most recent 90 seconds of recorded voice data are always be present.

The replay of the recorded voice data is activated by the replay button 15 on the front panel: A push on the replay button 15 causes a replay user interface window to be displayed in the graphic display 12. When the operator presses and holds down the replay button 15, the communications device displays a counter in the display 12 and increments the counter as long as the user holds the replay button pressed. The counter determines how many seconds of recorded data is to be replayed. When the operator releases the replay button again when the counter shows a value X, the replay function plays the last X seconds of received data.

During the replay time, the upper display 5 shows "--". The replay initially displays X, i.e. the number of seconds of data to be replayed, and "Press BACK to cancel replay." The displayed number counts down during replay until X=O is reached and the replay is automatically terminated. After termination of the replay function, the graphic display 12 returns to the status it was before the replay function was activated. The upper display 5 restores to display the working channel or frequency.

A renewed push on the replay button, while the replay function is active, terminates the present replay and takes the replay counter further back from the current replay data. When the replay button is released again, replay takes place from the new data position, which is also indicated by the counter in replay window. If the operator pushes any other key during the replay function, the replay function terminates.

In the present embodiment, incoming voice data (indicated by an open squelch) during replay does not have priority over the replay. If a call is received on the working channel/frequency while the replay function is active, the communications device displays an appropriate message on the display 12, e.g. "New Incoming Voice Data." Incoming data during replay is not recorded in the replay buffer. In an alternative embodiment, an additional buffer may be provided for this situation.

The volume control button 14 can be used on the replay data to adjust the sound pressure in audio devices.

An interesting application of the replay function described herein is in combination with a multi channel mode. In some embodiments, the communications device includes functionality for monitoring two or more channels. Examples of such functionality include a dual watch mode and a scanning mode:

The dual watch mode is a mode where a priority channel, e.g. channel no. 16 for distress and calling, is scanned periodically for a signal while listening on another working channel. In the example of fig. 2, the user interface comprises a button 19 for activating the dual watch mode. One of the indicators 4 is marked "DW" and indicates whether the dual watch mode is active.

Scanning is an extension to the dual watch functionality that allows the monitoring of multiple channels. For example, the device may provide one or more different scan types, e.g.:

• Scanning all available channels in a sequence • Scanning a number of selected channels in a sequence organized into one or more individual, user-configurable scan tables.

In the embodiment of fig. 2, the scan type is selectable via the menu functions. In scanning mode, "SC" is shown in the upper display.

If an active signal is found on a channel different from channel no. 16 the radio remains on that channel for a predetermined time, e.g. 10 seconds, where after scanning is resumed. The upper display displays the active channel. If an active signal is found on channel no. 16 the device is locked on channel no. 16 until the signal disappears, where after scanning is resumed. In this case, the upper display also displays the active channel, i.e. "16".

The scanning can be terminated by the operator by: • Lifting a handset (not shown) off hook; if scanning is terminated while an active signal is received, the device continues to operate on that channel after termination; otherwise it returns to the working channel that was active before entering the scanning mode.

• Pushing the button 16 for selecting channel no. 16 as working channel • Pushing DISTRESS (button 11 ) to initiate a DSC distress

• Pressing button 20 to switch back to the working channel that was active before entering the scanning mode.

• Pushing the replay button to initiate a message replay.

Hence, in such a scanning mode all incoming messages on any of the channels are recorded in the recording buffer, and the corresponding channel numbers or frequencies and date and time of receipt are stored in the message database. Hence, when the operator is temporarily unable to listen to the received messages, he/she may replay the most recent messages upon return. Fig. 3 shows a more detailed functional block diagram of replay function:

Recording of voice:

The communications device comprises a circular buffer 303 for recording received voice messages. The incoming audio signal 301 is fed into a squelch circuit 302. The constantly audio recording functionality is solely controlled by the squelch. If the squelch is closed it is assumed that the criterion under which the user wishes to receive audio is not fulfilled and the recorder 303 is not activated. As soon the squelch opens two things happen: - Firstly the buffer 303 starts recording the incoming voice signal 304 received via the squelch. The buffer is a RAM adapted to store the received audio signal as suitably coded audio data, e.g. as pulse code modulated (PCM) data sampled in 16bit/9.6kHz. Accordingly, the incoming audio signal is fed through a signal processing block 309 that generates the audio data to be stored in the buffer 303. The buffer is a RAM that is wrapped around, i.e. written in a circular fashion such that the oldest data is overwritten by the most recent data. The audio signal 304 from the squelch circuit is also fed via a switch 310 into an internal or external loudspeaker 311. - Secondly, when the squelch opens, it sends a trigger signal to a data record generation block 305 that generates a corresponding message information data package. The package consists of current time, date, and the current receiving channel or frequency. In this example, a peripherally attached GPS receiver 306 provides the date and time, and the operating system 307 of the communications device provides the channel information. It is understood, however, that the time information may also be provided by another source, such as an integrated GPS receiver, an external or internal clock, etc. The duration of the received message on the particular channel is determined when the squelch closes and forwards a corresponding trigger signal to the data record generation block. The duration is determined as the time difference between the opening trigger signal and the closing trigger signal. The data record generation block stores the generated data package in a package database 308. The package database can hold up to 195 packages that include the information on all voice messages in the recording buffer. The package database is written in a circular fashion, such that outdated entries are overwritten by more recent entries. The system determines which entries are outdated by summing the duration information for all entries in chronological order starting with the most recent entry. When the accumulated duration exceeds the duration that can be stored in the buffer 303, all older entries are outdated.

Replay of voice:

The operator initiates replay of the recorded voice messages from the buffer 303 via the loudspeaker 311 by first pressing the replay button 312. Pressing the button starts a timer 313 that determines how long the replay button is pressed. Hence the timer 313 is started when the replay button is depressed and stopped when the replay button is released again. The timer continuously forwards the timer result to a rewind time calculation block 314 that calculates an actual rewind time from the activation time of the button. The maximum rewind time corresponds to the buffer size, i.e. in this example 90 sec. If the actual amount of recorded audio in the buffer 303 is less than 90 seconds, the maximum rewind time corresponds to the actual amount of audio. The calculation block 314 determines the rewind time as a predetermined function from the activation time, i.e. the key-press time, of the button. For example, the rewind time calculation block may use the following relation between the rewind time and the key-press time, which allows a fast and accurate rewind:

For key-press < 3 seconds: Rewind time = 3 * key-press time For key-press > 3 seconds: Rewind time = 15 * key-press time. Hence, the activation time is multiplied by a scaling factor to obtain the rewind time, where the multiplication factor depends on the activation time. However, it is understood that other relations between the rewind time and the activation time of the button may be used. For example, the calculation block 314 may determine the rewind to be equal to the activation time of the button (up to the maximum rewind time), or use a constant multiplication factor that does not depend on the activation time.

The rewind time calculation block forwards the calculated rewind time to a graphical display 315 while the replay button is pressed, thereby providing a visual feedback to the operator indicating the rewind time selected so far. Hence, the operator may accurately select a desired rewind time.

When the operator releases the replay button 312 again, the rewind time calculation block 314 forwards the final rewind time to an index calculation block 316 that converts the rewind time to an index in the recording buffer at which the replay shall start. For example, the circular buffer may be controlled by two pointers/indices: A write pointer 317 indicating the start position for the recording of the next message, and a read pointer 318 indicating the position of the current replay. It is understood that the operation of the circular buffer may require additional indices, e.g. indices indicating the start and end of the buffer area, such that the read and write indices jump to the buffer start when they reach the buffer end. It is further understood that other indexing schemes may be used in order to implement a circular buffer. The index calculation block calculates the read index as a buffer position relative to the current position of the write index, such that the difference corresponds to the desired rewind time.

The replay function starts the replay of the recorded voice messages at the calculated read index 318 directly after the operator has released the replay button. The system reads the stored messages from the buffer 303 and advances the current read index accordingly. The read messages are fed into a processing block 319 that decodes the audio data according to the coding scheme employed, and generates an audio signal that is fed to the loudspeaker 312 via the switch 311. The replay stops when the rewind time has reached zero, i.e. when the current read index 318 has reached the current write index 317, unless the user wishes to stop the replay function, as described in connection with fig. 2.

While replaying the recorded audio, the device displays the corresponding time, date and channel information on its display, as indicated by display block 315'. It is understood that the displays 315 and 315' may be the same physical display. To this end, upon release of the replay button 312, the rewind time calculation block 314 forwards the calculated rewind time to a message information retrieval block 320. The message information retrieval block determines a database record in the message database 308 that corresponds to the calculated rewind time. For example, the message information retrieval block cycles backwards through the most recent message entries and accumulates their respective durations stored in the database, until the accumulated duration reaches the calculated rewind time. The message information retrieval block receives the thus determined message record/package, and causes the corresponding message information to be displayed on the display 315', e.g. date and time of recording, channel number or frequency of the communication channel over which the message was received, and message duration. During replay, the message information retrieval block further counts down, and displays on display 315', the remaining replay time. Based on the remaining replay time, the message information retrieval block further retrieves updated message information form the database 308, and dynamically updates the display 315' as the different received messages are replayed. As described above, the operator can terminate the replaying of audio by pushing an appropriate button, e.g. the MENU button 8, or the OK button 17 in fig. 2. In one embodiment, any audio signals received during replay, are neither forwarded to the loudspeaker (as controlled by switch 311), nor recorded into the recording buffer. However, the device indicates via its display when the squelch is open during replay, thereby indicating that there is incoming communication on the current channel/frequency.

Even though embodiments of the invention have mainly been described with reference to a VHF system, it is understood that the invention is not limited to VHF but that it may also be used in connection with other maritime radio communications equipment, e.g. equipment operating in the medium frequency (MF) and/or high frequency (HF) band.

The term radio-frequency communications channel is intended to refer to any wireless communications channel utilising radio-frequency communications signals. Within VHF radiotelephony a number of communications channels are distinguished by respective transmit and receipt frequencies and identified by corresponding channel numbers.

Claims

Claims:

1. A maritime radio communications device comprising

- a radio receiver for receiving voice messages via a radio-frequency communications signal;

- a recording buffer for recording a plurality of said received voice messages;

- a user-controllable replay means for replaying a user-selected one of said recorded voice messages.

2. A maritime radio communications device according to claim 1 , wherein the recording buffer has a predetermined storage capacity corresponding to a predetermined total recording time; and wherein the recording buffer is controlled to record all received voice messages such that the most recently received voice messages up to said total recording time are stored.

3. A maritime radio communications device according to claim 1 or 2, wherein the radio receiver comprises

- a receiver circuit for receiving a radio-frequency signal and to generate an audio signal from said received radio-frequency signal; and

- a squelch circuit adapted to control the recording buffer to record said audio signal as a received voice message only when the received radio-signal fulfils a predetermined condition.

4. A maritime radio communications device according to claim 3, further comprising processing means adapted to generate a message information data item for each recorded voice message, said message information data item being indicative of the position of the recorded voice message in the recording buffer.

5. A maritime radio communications device according to claim 4, wherein the message information data item comprises information about a duration of the voice message; and wherein the processing means is adapted to receive trigger signals from the squelch circuit indicative of a start and stop of the recording, and to calculate the duration from said trigger signals.

6. A maritime radio communications device according to any one of claims 1 through 5, further comprising a message database for storing a number of message information data items, each message information data item comprising information about one of the recorded voice messages.

7. A maritime radio communications device according to claim 6, wherein each message information data item comprises at least one of a channel number or frequency of a communications channel over which the voice message was received, a date and/or time of recording, and a message duration.

8. A maritime radio communications device according to any one of claims 1 through 7, further comprising a user-operatable activation means adapted to control the replay means; wherein the user-operatable activation means is adapted to receive a user-input indicative of a position in the recording buffer, and wherein the replay means is adapted to selectively replay one or more recorded voice messages responsive to the user-input.

9. A maritime radio communications device according to claim 8, wherein the replay means is adapted to retrieve a message information data item from the database based on the user-input, and wherein the maritime radio communications device comprises a display for displaying the retrieved message information data item.

10. A maritime radio communications device according to claim 8 or 9, wherein the user-input is indicative of a rewind time.

11. A maritime radio communications device according to any one of claims 8 through 10, wherein the activation means is adapted to detect a duration of an activation of said activation means by the user, and wherein the replay means is adapted to selectively replay one or more recorded voice messages responsive to the detected duration of the activation.

12. A maritime radio communications device according to any one of claims 1 through 11 , wherein the radio-frequency communications signal is a VHF signal received over at least one predetermined radio-frequency communications channel.

13. A maritime radio communications device according to any one of claims 1 through 12, adapted to be operated in a multi-channel mode, wherein the device is configured to

- regularly monitor each of a plurality of channels or frequencies as to detect incoming voice messages one each of said plurality of channels, and to

- receive and record in the recording buffer any detected voice message.