Draft for commentsRTCM Paper 186-2005-SC119-109
RTCM Recommended Standard For Maritime Survivor Locating Devices
Proposed Changes for Active MOB Devices
Reference –RTCM Standard 11901.0 (RTCM Paper 240-2004/SC119-STD) MSLD
Proposed Changes
# / Reference / Suggested text1. / 1 Scope, para 1 / Replace paragraph 1
This document specifies the minimum functional and technical requirements for a Maritime Survivor Locating System which may consist of Alerting Units, Base Unit, Position transducers, two way satellite link to shore and shore base facilities for mounting a search and rescue operation.
2. / 1. Scope, para 3, / Replace sentence 1
The purpose of the Base Unit is to recognise an alert (however generated) and raise the necessary alarm conditions when a crew member with an Alerting Unit goes overboard. The Base Unit may communicate this information to a shore based station via an appropriate wireless link.
Sentence 2 & 3 – no change
3. / 1. Scope, para 4 / Replace sentence 1 with these two sentences -
The Alerting unit typically consists of a radio transmitter, an integral antenna and a power source all contained in a wearable watertight case. The internal unit may also be fitted with a radio receiver, a rechargeable power source, a data processing unit, visual and tactile indicators and operating control(s).
Sentence 2 & 3 – no change
4. / 3.1 Definitions / Replace definition of Maritime Survivor Location Device (MSLD)
A Maritime Survivor Locating Device is a system which comprises of one or more Alerting Units, one Base Unit, an optional two way ship to shore communication mechanism with ability to send vessel position, speed, heading and send/receive other useful data
1)Alert – The Base Unit shall be capable of recognising an alert condition either through an absence of signal, or by an alert signal from the Alerting Unit.
2)Alarm – The Base Unit shall provide on-board alarm to notify crew of an overboard incident. An option to silence or cancel the alarm should be provided. When fitted with shore base communication apparatus the Base Unit must transmit the alarm data to the shore station if the alarm is not cancelled within a given time period
3)No change
No change to paragraph “Depending on the MSLD … “
5. / Replace definition of Alerting Unit
A device carried or worn by a person which communicates by radio with a Base Unit and depending on the algorithms and schemes employed by the system enables the Base Unit to,a) recognise a Man Over Board incident, b) receive a manually generated emergency alert and c) optionally determine if the person is inside or outside a protected area
6. / Replace definition of Base Unit
A Base Unit is a device which communicates with one or more Alerting Units and is able to determine if a person wearing an alerting device is either on board or not on board, or inside or outside a protected area. Optionally, when suitably fitted and configured, the Base Unit is also capable of two way communication with a shore based station in order to transmit/receive vital information (e.g. lat/lon, speed, heading etc) for launching search and rescue operations if deemed necessary
7. / Amend Locating Function
Locating function may be provide by either one or both of the following methods –
1)No change to “The AU provides means ….. separate from BU may be used”
2)New – The Base Unit provides distance and course to steer in order to locate person in the water
8. / 4.1 Control and Indicators / Replace sentence “AUs should be designed for manual activation … “ with -
The system should be capable of manual activation in case of an emergency from either the Base Unit or the Alerting Unit, and automatic activation should a person wearing an Alerting Unit goes overboard
Amend paragraph “Not less than two simple …. “ to –
Activation should consist of at least these methods -
1)Activation from Alerting Unit – Use existing paragraph “Not less than two simple, independent actions …. Or two independent switches”
2)Activation from Alerting Unit – A suitably marked control on the Alerting Unit must be operated for 5 seconds in order to generate an alert which must be recognised by the Base Unit
3)Activation from Base Unit – Two independent actions on the Base Unit must be performed to generate an alert, e.g. lift cover over a switch marked “Alert” and then holding it down for 5 seconds.
Alert cancellation – A mechanisms must be provide for cancelling false alerts
Silencing of alarms – A mechanism may be provided for silencing audible alarms without cancelling the alert
9. / 4.1.2 / Amend section to read as follows
A MSLD system provided with both automatic and manual activation, should have as a minimum, clearly marked controls to operate the devices in the following modes –
Non-Alerting – In the non alerting mode all alerts are off and an alert is raised when a person wearing an Alerting Unit enters the water or when there is a manual activation.
Alerting – The system enters alerting mode when an Alerting Unit enters the water or when the Alerting Unit is outside the protected area, or when the Alert control on either the Alerting Unit or Base Unit is operated in a prescribedmanner. Once alerted, the system must remain in alerting mode until the alert is cancelled by operating a control provided for this purpose. It is not sufficient to use procedures such as short-circuiting of water contacts, removal of power supply, etc. to instigate or cancel an alert.
Alert Cancellation – A control for cancelling the alert should be provided. When this control is operated all alerts and alarms are turned off.
OFF – In OFF mode, the MSLD system is deactivated (the system is neither in Non-Alerting or Alerting mode)
Test – No change
10. / 4.1.4.1 Alerting / Replace paragraph with –
The system should recognise an alert within 60s and the Base Unit should sound an audible alarm with a minimum sound output of 85 dBA when measured 30cm from the Base Unit. In addition, an indicator on the relevant Alerting Unit should turn on, be visible in direct sunlight, low light and no light conditions and must remain on unless turned off through manual intervention or until the battery is discharged
11. / 4.1.4.2 Self Test / Amend existing paragraph as follows –
“When an alert from an Alerting Unit is recognised by the presence of a signal, then” + “A visual and/or audible indicator …… the self-test is in progress”
When an alert from an Alerting Unit is recognised by the absence of a signal, then the Alerting Unit must provide visual or tactile or audible indication to show that connectivity with other devices within the MSLD system has been lost.
12. / 4.2 Self Test / Replace section with –
The MSLD system should be provided with a self test feature operating at regular intervals and throughout the temperature range for the following –
- Battery
- Altering Unit to Base Unit Connectivity and/or RF output from Alerting Unit
13. / 4.2.1 Battery Self Test / Move paragraph “The manufacturer should verify the ….. during self test” to section 8 as this is part of design verifications
Amend 2nd paragraph to -
The battery self-test should indicate when the battery is no longer capable of providing minimum operating time or in the case of a rechargeable battery when it should be recharged
14. / 4.2.2 RF Self Test / Add following sentence –
In a system that depends on a transmission of an alert signal for an alert to be recognised, then the following RF self-test requirements shall apply -
15. / 4.3 Buoyancy / Amend paragraph to –
Unless the AU is intended to be incorporated into a buoyant device, it should have sufficient positive buoyancy to float in fresh water and should provide the system with its intended functionality while floating in fresh or salt water
16. / 4.4 Environmental Factors / Replace first sentence with –
The AU must not be damaged and must provide the intended functionality when subjected to the following –
No change to remaining text
17. / 5.2.2 Battery life for primary battery / Change title of section to “Battery life”
Make all existing text as part i), and add following to start of 1stparagraph –
When non rechargeable batteries are used then ….
Add following paragraph after last paragraph as part ii) –
When rechargeable batteries are used the MSDL system manufacturer must establish a minimum useable duration between recharge cycles.
18. / 5.3.2 Identification and Instructions / 1st paragraph, replace “All labelling” with –
All markings and/or labelling
Change point g) to –
Self test instructions if applicable
19. / 6.1 Lifesaving Equipment / Change title of section to “Lifesaving”
Replace paragraph with following –
The MSLD system may include one or both of the following functions –
1)Remotely launch lifesaving equipment from the vessel, either automatically or by remote command
2)Launch search and rescue operations from any vessel or from a shore based station after verifying alerts from the MSLD system
20. / 8.1.7 Battery capacity and low-temperature test / 1st paragraph, 1st sentence, amend -
Using a fresh battery pack or a fully charged battery (when rechargeable batteries are used),the Alert Unit should be operated under normal test conditions for a period ……
2nd paragraph, 3rd sentence, amend –
The unit should be operated within 30 min ……
Annex D
(normative)
Active Signalling Type MSLD System
D.1 Operational Scenario
Unless there is an alerting system on a vessel (or on the shore), a person falling into the water may go un-noticed and the whereabouts of this person could easily become unknown within a very short period of time.
The Active Signalling Type MSLD System (A-MSLD) provides a mechanism of operation where received signals indicate non-alerts and absence of signals indicate an alert.
When a person wearing a signalling device known as an Alerting Unit falls into the water, the signals from the Alerting Unitare assumed to be sufficiently attenuated by the water, thus creating an absence of signals. The A-MSLD system recognises this absence as an alert. This fail safe embodiment places no requirement on the Alerting Unit to be buoyant.
D.2 Definitions
- Type 1 error – Type 1 error occurs when a valid Alert is not recognised by the system
- Type 2 error – Type 2 error occurs when a false Alert is generated.
D.3 System Components
The system has two essential components as described below
1. Base Unit
Each A-MSLD system must have one Base Unit (BU). The BU monitors signals from the Alerting Unit(s) and keeps the system in the non-alerting mode when signals from an AU are being received and places the system in alerting mode when signals from the AU(s) are interrupted.
In Alerting mode the BU would provide the necessary indicators and alarms which may be silenced by operating dedicated control(s).
The BU may also be fitted with the following capabilities –
- Backup battery within the A-MSLD system to ensure continued operation for a certain duration in situations where vessel’s battery power is lost
- Ship to shore communications to transmit alerts to a shore based station to enable appropriate rescue operations to be mounted.
The BU communicates with the AU using a licence free type approved ISM Band (2.4 GHz)RF technology and a suitably configured network topology. Suitable systems are:
i)IEEE 802.11b WLAN Ethernet (Wi-Fi)
ii)IEEE 802.15.1 Class 1 WPAN (Bluetooth)
iii)IEEE 802.15.4 WPAN (ZigBee)
2. Alerting Unit
The Alerting Unit (AU) is worn by a person who will need recovery should he fall into the water.
The Alerting Unit is a watertight unit which continuously transmits signals that are monitored by the BU. When the AU goes into the water, its RF signals are sufficiently attenuated by the water to stop communication with the BU thus generating an alert at the BU.
The AU has visual indicators to show alerting and non-alerting modes, and has control(s) to raise a manual alert.
The AU may optionally be fitted with a locating device.
D.4 Performance Characteristics
1. Operating time
The A-MSLD system should meet the following operating durations –
- With fully capacity batteries, the AU should operate for a minimum of 12 hours. The system should provide for a low battery indication.
- The BU should be capable of continuous operation from the vessel’s supply, and for 6 hours from a fully charged backup battery in the absence of the vessel’s supply.
2.RF Coverage and connectivity
The BU and all AUs worn by the users must maintain connectivity at all locations on a vessel where protection is required.
In an installation where the AU has no connectivity due to say some structures on the vessel or distance, then additional BU Repeaters (BUR) must be provided to maintain continuous coverage.
The A-MLSD system should allow for at least three BU Repeaters to be fitted to the system in order to ensure adequate coverage on the vessel. Star or mesh network topology (or a combination of these) may be used as deemed fit by the manufacturer.
When BUR(s) are fitted,network arbitration between BU, AUs and BURs should be automatic. Interruptions and delays should be designed to keep errors within the prescribed limits.
D. 5 Errors
Type 1 error (when a valid Alert situation is not recognised) rate must be zero.
Type 2 error(false alert) must be less than x for every 10000 hours[m1] of operation.
D.6 Type Approval Requirements
The choosen WLAN / WPAN system used in the AU, BU (and if applicable BURs) shall be approved to the relevant IEEE 802.XX.X standard and there shall be evidence to this effect.
The effective operation of the system shall be demonstrated by simulating a Manoverboard alert using an AU and determining that the alert is registered at the BU within [60] seconds.
The manufacturer shall propose a scheme to demonstrate that the False Alert rate for the system is within the limits set for a Type 2 error in section D.5.
Further requirements to be developed[CPH2].
2005 12 02 RTCM MSLD Active Device ProposalPage 1 of 8
[m1]Needs much debate
[CPH2]Need to debate how detailed to make this section