PDoc-Network Protocol - LSCES Main Site

Network Train Describer Protocol

Broadcast information for the Network Train Describer (TD) will be based loosely on BR1810, and will implement appropriate commands from that protocol in addition to functionality required to maintain slave copies of the running timetable on remote sites, and update information not directly supported by normal TD operation. Since the TCP/IP transmission protocol does not require some of the communications support built into BR1810, only the messaging structure needs to be provided. In addition, the connectionless nature of UDP based Broadcast TCP/IP requires the addition of a message number in each packet sent, in order that all slave receivers can detect missing packets from the sequence. One problem that will need to be addressed is that a single packet may be transmitted, but can be received as several packets. This depends on the configuration of the network hardware, which should be programed not to break up single packets. This may not be possible but the question needs to be asked.

Basic Packet

A four digit number is used to provide this ID although a smaller number would be adequate. The first letter will be reserved for a group header identifying one of a number of sources all feeding information into the system. This message ID is followed by the General Message Classification Character, and the sub-classification character. This leaves a maximum of 1500 characters of data which may be packet into a single packet.

SNNNXY<--Data-->

The spare 'U' group of Message Classifications will be used for Running Timetable management, since no accurate details are available for the 'T' group which is designated "Timetable system - service amendments". Support can be easily be switched to the recognised commands should this prove necessary, but it is anticipated that the information provided will exceed that originally planned for in BR1810. The main reason for maintaining compatibility is for the transmission of movement information directly from the TD sources to the network.

The group 'O' commands are implemented for running LLPA and recorded announcements.

Commands from the 'C' group will be supported as necessary, 'H' group is used for network time, and 'W' group will be used for test purposes.

Handshaking

Two network ports will be set up in the same manor as SNMP. One will be used for broadcast out, while the other will be monitored for replies from remote sites. When a packet is received out of sequence, a remote site will post a message requesting the missing packet. This area will probably need some adjustment, such as implementing a timeout to allow out of sequence packets to arrive.

The normal traffic will not be acknowledged, but the time message may be used to provide a check that all sites are accessible. If two successive minute tick messages are not received, and there is no other network traffic, then the site will try and connect back.

STTTTTCC111222333444555666777888HHHHHHHH

S - Source ( Used to indicate additional Management sources such as additional EquipmentManager programs )
TTTTT - Tag number of the Local Hub initiating the reply
CC - Command being returned
111 to 888 - Reply bytes for programs 1 to 8 - Consists of Program Letter, Program Status, and a Reply byte.
HHHHHHHH - Status of Local Hub

The Program letters relate to the entries for programs in the Tag 10 to 36 area of the EQUIPMENT database. This can be configured as required for the system being created, with a restriction that a maximum of 8 programs can be managed.
The program status is the value to be loaded into the STATUS field of the EQUIPMENT database.

-1 Disabled (Gray)
0   Not Running (Fuchsia)
1   Normal (White)
2   Fault (Yellow)
3   Not Answering (Green)
4   Not Detected (Red)
5   Starting Up (Olive)
6   Updating (Teal)

Status 5 and 6 would normally only be returned by LocalHub.

The function of the Reply byte has yet to be defined, and will be a combination of standard messages with some program specific variations.
The top bit being set will indicate program specific error messages ( 128 to 255 ), while 0 to 128 will be normal status messages.
When a Local Poll Reply is received, the program status will be updated on the basis of the top bit of the reply byte. If set, then a fault reply will be reported, otherwise a Normal reply is logged. LocalHub sets all programs to state 3 when generating a Local poll, and this is cleared if a Local poll reply is received before the next minute refresh. Programs that have been manually stopped do not respond to the local polls, and no fault is generated, only the Not running reply.

The first byte of the local hub status will contain the same Reply byte, and the following 7 bytes allow further information to be added if appropriate.

Restarting a Hub will generate an unsolicited poll message which will be used to indicate to equipment manager that a machine has restarted, and subsequent poll replies will provide updates on its startup progress. This poll reply has a status of Starting Up, and similar poll replies

Time messages

The normal TD operation is to post time in response to a request message. The basic Network TD will provide an HU message every minute within 5 seconds of the actual Rugby tick. This message may be the only activity on the network, and its record number will confirm no messages were transmitted in between. If messages are outstanding, then the system will wait for a second tick before chasing the missing message.

SNNNHUhhnnssddmmyyyy

The spaces are introduced to provide easy reading on monitor programs.
S - Source ( Used to indicate additional Management sources such as additional EquipmentManager programs )
NNN - Message number
HU - Command
hh - hour ( 24 hour clock )
nn - minute
ss - seconds
dd - day ( include 0 if necessary )
mm - month ( include 0 if necessary )
yyyy - year ( y2k compliant )

On receipt of this message, the remote site will generate a reply message saying that it is awake, which will update the status in the master EQUIPMENT database.
If the reply is not received within the next minute, then that site is flagged as not responding.

Local Messaging

Messages and replies are carried between the LocalHub and the relevant local program module by the use of local messages relayed on their own local port number. This is identified as an offset of the program number from the Local Listen port. Local messages omit the NNN message number and use the program number as the S designation. Most messages are relayed back to the Equipment Manager for forwarding, but some are intercepted and processed rather than relaying them. The following start and stop commands are translated into local commands depending on the program status in the LocalHub. All programs create a Stop message which updates the LocalHub running status, but which is not relayed on to the network. In order to prevent conflict with Stop messages such as those relayed to the ClockSlave program to switch them off when a global shutdown is required, an additional pair of start/stop commands ( XH and XR ) are only used on the local connection and are translated to XS and XK commands for the network.

A Local copy of the HP message is propagated to all local programs, and a simple single byte reply is generated. This has been detailed in the handshaking section above.

Remote Start Messages

There are three types of remote start message, one of which has no extensions, one has a single number, while the third requires a computer ID and program number.

SNNNXS

Will request that all remote programs start. Listener will start each module in order, waiting for the first module before proceeding to the next. The next poll request will see the state each program is in.

SNNNXSn

Will start the global program number n if it is associated with the program table for a listening machine. This would, for instance allow all copies of DCSlave to be started.

SNNNXSsssssn

sssss - station number / equipment tag
n - program to start

The tag number is taken from the EQUIPMENT list, if it refers to a particular computer, then the program number relates to that computers program entries, but if the tag refers to a station then the global program entry is started on all machines on that station.

Remote Stop Messages

Replace the XS above with XK in order to stop the relevant program or set of programs.

SNNNXK will cause all machines to be returned to their boot state.

(Using an XX will activate a power on reset for a device if the facility is available)

The following section has been left in for reference to how train timetable and movement information could be added to the system. The document is loosely based on the TD message formats, and so TD messages can be transfered on from any source to the rest of the system, where they will carry out the correct update of information.

Messages for Retransmission

All local hub messages are sent to the Network Hub, provided by EquipmentManager-Master. These messages take the same header format as the handshake, but contain the message detailed below.

STTTTTCC<Command Information>

S - Source ( Used to indicate additional Management sources such as additional EquipmentManager programs )
TTTTT - Tag number of the Local Hub initiating the reply
CC - Command being returned

This modification is required to reduce the amount of multicast activity. Only the Network Hub now uses Multicast to output messages, and all local slaves forward these messages via the Network Hub.

Timetable Update

The provisional facilities of the 'U' command group are as follows.

UA - Add / Update Text File
UB - Spare
UC - Change Status
UD - Delete Train Record
UE - Spare
UF - FTP File Transfer
UG - Spare
UH - Add / Update TIPLOC
UI - Insert Calling Point
UJ - Update Calling Point
UK - Delete Calling Point
UL - Spare
UM - Spare
UN - Add / Update Train Record
UO - Add / Update Train Record Calling Points
UP - Change Platform ( May use 'P' group for additional control functions )
UQ - Spare
UR - Spare
US - Change Sequence
UT - Change Termination
UU - Update Train Record
UV - Spare
UW - Spare
UX - Remote Control
UY - CIF Extract Flag
UZ - TD Arrive and Depart

Messages will be built using a few basic message formats, using standard format elements.

<TIPLOC> - This is a 7 character field as defined in the Tiploc table. All station names will be transmitted using this shorthand, and the full display information will be expanded using a look up table at each site. ( See UH for updates to Tiploc Information ). In order to reduce the size of the working copy of TIPLOC, only records with a type entry set will be used. The master TIPLOC table from a CIF extract has the station entries flagged as zero, and these are switched to 1 for any records that are present in the extracted timetable. Records with a type > 1 are added and maintained locally to the system.

In order to cater for additional expansion of the system, a number of additional TIPLOC codes are defined. These start with non-alphabetical characters and are used to define Notes ( '#xxxxxx' ), Managed Messages ( '@TTxxxx' ), Temporary Messages ( '$ssxxxx' ), Split Station Designations ( '/xxxxxx' ), and Station Grouping ( '=gxxxxx' ). Notes and Split Station details form part of additional lines in a calling point pattern, and there content is managed in much the same way as individual stations in the TIPLOC list. Notes are also used to manage individual pages of information for which special notices, and associated announcements exist. In order to use these message pages efficiently, a grouping system has been introduced contained within the seven characters of the TIPLOC.

Notes ( '#xxxxxx' )

These entries are used as additional lines in NTI Calling Point lists, or else where.
The long and short text alternatives are stored in the TIPLOC table and have a type entry of 3.

Managed messages ( '@TTxxxx' )

where TT is the ATOC Code, allowing grouping of managed message by TOC. The first x could be used as a type flag -similar to the profile management.
Details for the messages will be added to the TIPLOC table, with a type of 4.

Temporary messages ( '$ssxxxx' )

The ss number will be taken from the system setup, to allow multiple operator positions.
Any files starting "$" will be deleted as part of system cleanup.
There will be no TIPLOC entries relating to these entries as they will not be expected to persist.

Split Station Designations ( '/xxxxxx' )

This is a special type of station name entry. It will be used by the CIS system as the destination for train records to split locations, and will then be omitted from the Calling Point List.
The text expansion is provided in the TIPLOC table, where the type entry is 2.

Station Grouping ( '=gxxxxx' )

The grouping system allows eight groups of thirty stations to be defined, with group 9 being used to define a global function to all stations.

The 'group' TIPLOC is built up as follows. First character '=', ( other characters can be added if required for expansion ). The second character is a number indicating which group, 1 to 8, with 9 indicating all groups. The following 5 characters are used as a binary map of which station to include in the group. Six stations are flagged in each character, with the top two bits of each character set to '01' to maintain compatibility with serial link transmission. In this way any combination of stations within a group can be selected. The LocalHub will decode the group message, based on its TIPLOC and Site Number, and will forward the message to Local programs if it is addressed. All replies will be made using the station number of the site ( this will be LocalHub TAG where more than one machine is running on a site ).

<RECORD NO> - This is a 8 digit numeric field holding the record number from the master RUNNING timetable. It is used as a unique identifier, and removes the need to cater for duplicate headcodes.

<HEADCODE> - This is a 4 character field. It is used where the actual train record is not known, and needs to be converted to a record number identified in the master RUNNING timetable. In the case of duplicate entries, the route and time information should allow selection of the correct <RECORD NO> to be used in place of the headcode.

<TIME> - All time fields are 4 character 24 hour clock information. Date information is recreated based on relation to the current time allowing the full date/time detail to be rebuilt as required. ( There may be a need to add a fifth character for the half minute flag used in SCHEDULED times).
<PTIME> Public time
<STIME> Scheduled time
( Exact requirements for Public and Scheduled times still need to be established )

UA - Add / Update Text File

In order to make changes to Special Notices, Connection and Ticket Validity Messages, and display profiles, the raw information is transmitted as required using FTP. The message is used to signal a change to the LocalHub if required to update locally generated page sequences.

SNNNUAxxxaaffffffffffffffff

xxx - File type ( See table of Profile directory entries )
aa - TOC Code for operator specific pages

If the first two fields are blank, then the file is stored directly in the \TEXT directory, otherwise the information is routed to the correct profile subdirectory. Profile information which is not TOC specific can use all 5 characters i.e. V168H.

ffffffffffffffff - File name as used by the system. This is only limited to 16 characters to reduce all entries where file names are used.

UC - Change Status

This command is implemented via the use of a UU message updating the whole record. If needed, the smaller correction messages will be added later.

UD - Delete Train Record

Delete the train record and its calling point plan.

SNNNUD<RECORD NO>

UF - FTP File Copy

Delete the train record and its calling point plan.

SNNNUF<DIR>[<SUBDIR>\]<FILE NAME>

DIR - Base directory to copy from and too.

Currently five directory locations are supported. The Program Directory and four data directories.

PR will copy from the system program directory to the local program directory as identified by the [Program] registry entry. The default location is c:\Program.

The four data directories all start with a D. DR for Profile, DP for Picture, DT for Text and DS for Sound.

The data directory is identified as C:\XXX\Profile etc. Where the XXX is the server machine name on the source end, and the local machine name at the local location. This mechanism is required because the stations can have different settings for Profile information and Pictures for each site. The copy procedure will only copy generic files to all locations at the present time.

SUBDIR - This is optional, and allows Formats or Page types to be downloaded to the correct sub-directory

Display formats such as H43S, V169, etc are supported along with DVC. In addition, extra page information such as TVM and CNM are also stored in subdirectories of the main data directories, and can be duplicated as required.

FILE NAME - Full file name including extension. This is a variable length, but the total message data must not exceed 64 characters. This allows 62 character files in the base directory, but shorter file names when the subdirectory is included.

Local Hub will pull the specified file from the the designated FTP server. Identified in the System registry settings.

UH - Add / Update TIPLOC

While the main server will maintain a complete copy of all TIPLOC codes, only those in active use will be copied to the remote sites. This command allows for amendments to be made to the remote copies.

SNNNUH<TIPLOC><LONG_TITLE><SHORT_TITLE>

If the TIPLOC is not found then it will be added with a USE code as follows, based on the first letter of the TIPLOC ( see TIPLOC format above )

/ = 2 split station destinations
# = 3 text notes line
@ = 4 stored announcement
Any other first letter will be added with a USE code of 1

UI - Insert Calling Point
UJ - Update Calling Point
UK - Delete Calling Point

These commands are implemented via the use of a UU message updating the whole record. If needed, the smaller correction messages will be added later.

UN - Add / Update Train Record

This command will add a train record to the local timetable without checking that it already exists. It is used to implement <New> and <Copy> commands from the operators screen, and produce additional records to display..

SNNNUN<RECORD NO>

If the record already exists, it is deleted prior to duplicating from the Master Copy of RUNNING.

UO - Add / Update Train Record Calling Points
UP - Change Platform

These commands are implemented via the use of a UU message updating the whole record. If needed, the smaller correction messages will be added later.

US - Change Sequence

This is implemented as a refresh request of the SEQUENCE and SUBLIST tables for a site.

sss = 000 then both SEQUENCE and SUBLIST are refreshed. Use will indicate if the sequence should be added to remote copies and sources are ignored.
sss = 001 to 009, the USE tag and sources will be updated, and the relevant used SUBLIST will be refreshed.
sss = 010 to 899 spare.
sss = 99x will be reserved for Global Control of sequences.

If running in a remote mode, only sequences listed in the local list will be refreshed.
For type = 000 commands, if use = site number then the sequence is added to the remote copy if missing, if use = 009999 then the sequence is added to all copies.

SNNNUSttttttsssuuuuuu1111111122222222

tttttt - Sequence Tag Number
sss - Sequence Type - Also used to flag type of update
uuuuuu - Use Tag Number
11111111 - Text for SOURCE
22222222 - Text for SOURCE2

UT - Change Termination

This command is implemented via the use of a UU message updating the whole record. If needed, the smaller correction messages will be added later.

UU - Update Train Record

If the record number exists in the LOCAL timetable, then its contents are updated from the MASTER timetable. The message is triggered when ever there is a change

SNNNUU<RECORD NO>

If the record already exists, it is deleted prior to duplicating from the Master Copy of RUNNING.

UX - Remote Control

This is used to action the relevant event for a train record at a remote station.

SNNNUX<RECORD NO><TIPLOC>b

b - is the button number to be activated.
0 = Update ( Rebuild NTI and Summaries )
1 = Pre-post ( Future compatibility - it is button 1 )
2 = Post ( Unpost if train is posted )
3 = Depart ( Ignored if already departed )
4 = Spare

UX commands act as a UU command

UY - CIFManage Extract

CIFManage <Extract> generates an update message, which will cause local hub to copy those additional train records.

SNNNUY<START RECORD><END RECORD>

<START RECORD> = nnnnnnnn
<END RECORD> = nnnnnnnn

The start and end record numbers indicate the range of record numbers added. These are not actually used at present, as the remote outstations will modify there activity based on the volume of traffic. A look ahead time, and number of records has been added to help spread the larger volume period into quiet times. Actual operation has yet to be finalised.

UZ - TD Arrive/Depart Message

This message is created by TDSlave in response to TD messages received. Filtering of Berth numbers and processing to platform numbers is done by reference to the BERTH table in EQUIPMENT. This command will be expanded to include a station TIPLOC later to provide position information.

SNNNUZ<HEADCODE><PLATFORM>

<HEADCODE> = ncnn
<PLATFORM> = nnn
The maximum number is 63, but offsets of 64 are added to indicate secondary platform information such as Front, Middle & Rear or First & Second. The offset number will be used as this is what is stored in the RUNNING database.

Announcement Control

The provisional facilities of the 'O' command group are as follows.

OA - Make a general announcement
OB - Spare
OC - Configure an audio channel
OD - Spare
OE - Spare
OF - Immediate announcement
OG - Spare
OH - Spare
OI - Spare
OJ - Spare
OK - Kill Announcements ( Blank Displays )
OL - Spare
OM - Spare
ON - Spare
OO - Spare
OP - Make a Train Record announcement
OQ - Announce a text file
OR - Spare
OS - Status reply from a completed announcement
OT - Spare
OU - Spare
OV - Spare
OW - Spare
OX - Spare
OY - Spare
OZ - Spare

Messages will be built using a few basic message formats, using standard format elements as listed in the Timetable section above.

OA - General Announcement

This is used to action the relevant general announcement at a remote station or stations.

SNNNOA<TIPLOC1><TIPLOC2><CONTROL>

TIPLOC1 will either be a single station or a station group to which the announcement will be made.
TIPLOC2 indicates the announcement to be made. Display pages will be linked to the announcement where required, such as Closed and Evacuate, and will override the normal display sequence on the station.

CONTROL will need to be defined, in relation to the zoning and control interface at the station. While a single length message would be nice, it may be necessary to define two or three different control groups depending on the PA system at a site.

For starters, a simple four byte control command is planned. A single '>' with the three bytes required by the simple outstation following

Character 1 - Additional zone selection set if more than 8 required, or address information form multiple channel systems.

Character 2 Zone selection

Most Significant
Bit 7    - Zone 8
Bit 6    - Zone 7
Bit 5    - Zone 6
Bit 4    - Zone 5
Bit 3    - Zone 4
Bit 2    - Zone 3
Bit 1    - Zone 2
Bit 0    - Zone 1
Least Significant
Selecting none will not prevent announcement from being activated, allowing additional connection to sound channel to remain active while outstation is not used.

Character 3 Status

Most Significant
Bit 7    - Spare
Bit 6    - Spare
Bit 5    - Override Night Setting ( Select daytime setting if night time mode, otherwise no effect )
Bit 4    - Override Local ( Disable Local Microphone, and start announcement - normally waits for local microphone to complete )
Bit 3    - Repeat ( Adds second copy of announcement to announce queue )
Bit 2    - Spare
Bit 1    - Spare
Bit 0    - Spare
Least Significant

OC - Channel Configure

This is used to configure the audio mode control at a remote station or stations.

SNNNOC<TIPLOC>HHMMHHMMX

TIPLOC will either be a single station or a station group which is to updated.

The first time will indicate the start of day time working and the second time will indicate the start of night time working, The final X indicates the mode to be selected for night time working ‘0’ for no change, ‘1’ for low volume, ‘2’ for short working, ‘3’ Both low volume and short working.

OF - Immediate Announcement

This is used to copy a sound file to a remote station or stations and action the announcement once received.

SNNNOA<TIPLOC1><TIPLOC2><CONTROL>

TIPLOC1 will either be a single station or a station group to which the announcement will be made.

TIPLOC2 indicates the announcement to be made. Display pages will be linked to the announcement where required, such as Closed and Evacuate, and will override the normal display sequence on the station.

See the OA command for details of the control bytes

Local Hub will pull the specified file from the the designated FTP server. Identified in the System registry settings.

OK - Override Announcements

This is used to kill announcements at a remote station or stations.

SNNNOK<TIPLOC>c
TIPLOC will either be a single station or a station group which is to be controlled.

c = Sub-command
0 - Clear any override ( used to unlock a previous 9 )
1 - Stop any current or queued announcements
9 - Lock out announcements. (This could be used to prevent local operation of the PA system )

OP - Train Record Announcement

This is used to action the relevant announcement for a train record at a remote station or stations.

SNNNOP<TIPLOC><RECORD NO>c<CONTROL>

c - is the type of announcement to make
0 = Kill any announcements relating to this record
1 = Pre-announce ( Message depends on status of train - Cancelled, Delayed, x Late )
2 = Approach
3 = At Platform
4 = Spare

If the <TIPLOC> is a group command, then each station that the train record has not yet reached will receive the announcement, if that station is enabled in the group list. It is up to the head end to ensure that the correct group of stations is actioned, and this will be linked to the route management system.
Need to decide if stations that have been passed respond with a 'not-needed' for a complete reply to the request, or only stations that actually announce make the reply.

If the record number is not in the local copy of running, the message is ignored ( ? should an NA reply be created ).

The control group is detailed in 'OA' and is subject to future enhancement.

OQ - Text File Announcement

This is used to action the relevant announcement of a text file using text to speech engine at a remote station or stations.

SNNNOP<TIPLOC><CONTROL>[<SUBDIR>\]<FILE NAME>

The control group is detailed in 'OA' and is subject to future enhancement.

SUBDIR - This is optional, and allows CNM and TVM type files to be accessed from the correct sub-directory

FILE NAME - Full file name including extension. This is a variable length, but the total message data must not exceed 64 characters. This allows 50 character files in the base directory, but shorter file names when the subdirectory is included. The base directory that is used is the local TEXT directory, and two different types of file are supported. The normal formated .TXT files are handled, along with a simple .ANA format, which just stores and converts raw text from the file direct to the engine. The .TXT files are announced with a 'wrapper' of text based on the particular file blank that is being used.

OS - Status Reply

This is used as an additional response from a remote station when a triggered announcement has cleared. It is also used for unsolicited reports from a remote site to update network information on the state of a site.

SNNNOSsssssnnn

sssss - station number / equipment tag
nnn - status reply

The detail of this command has yet to be decided. It is anticipated that local actions will be flagged by these messages, if a fast network connection is available, otherwise only actioned events will be responded to. When an announcement message has been generated it will be flagged in the EQUIPMENT database, and the related reply will clear that flag. See the notes on OP relating to messages from 'not required' sites, some additional work may be required centrally to identify which sites are expected to respond.

The reply will be used in conjunction with the LocalHub poll reply. General availability information will be contained in the program reply bytes for the particular program this is either interfacing to the PA system, or generating the audio within the local machine.

General Purpose Message Group

To facilitate inter program messaging, the Q Group of commands is reserved for this function. This group of commands will be transfered transparently through the Local Hub, echoed back via Equipment Manager. A message package with a maximum size of 64 characters will be catered for in this version.

QR - Refresh Message

This is used to signal to slave programs to refresh or update the specified equipment tag.

SNNNQRttttt

ttttt - equipment tag

The first application of this command is to allow the CMSOnline program to flag to the CMSTerminal program that a ticket or staff member has been cleared from the specified terminal number. The CMSTerminal program will process this as a <X> command from the terminal, and will result in the obsolete information being cleared from the terminal screen.

QS - Focus Message

This is used to signal to slave programs to bring themselves to the front. It is intended to focus an application when either central control has overridden local activity, or a message of high priority is required to be actioned.

SNNNQSn

Will focus the global program number n if it is associated with the program table for all listening machine. This would, for instance allow all copies of CISOperator to be brought to the front when an evacuate notice has been activated from the control centre, giving all remote operators a direct indication of the situation.

SNNNQSsssssn

sssss - station number / equipment tag
n - program to focus

Local Message Group

To facilitate local inter program messaging, the W Group of commands is reserved for this function. This group of commands will be transfered transparently through the Local Hub, but will not be transmitted to echoed back via Equipment Manager. A message package with a maximum size of 64 characters will be catered for in this version.

W* - Basic Message

This is used to signal to slave programs to refresh or update the specified equipment tag.

SNNNQRttttt

ttttt - equipment tag

The first application of this command would be to provide local switching between programs where the normal <Alt><Tab> function is not available such as where the control station is only provided with a touch screen. ( At present the QS message is being used, but this is somewhat 'heavy' for simple local actions, and so it is planned to provide a WSx command to implement this function.

Issue j- 26/03/2002 - Correction to OP command to align TIPLOC with other commands.
Issue k - 25/04/2002 - Add OQ command.
Issue l - 31/01/03 - Adjusted the format of the Announcement 'Control' message to remove older format restrictions in line with newer PA capabilities.
Issue m – 01/03/03 – Spellchecked!, included W group, corrections to a few incorrect expansions.