WB1400 HANDEL Page 1 of 2

This topic describes the second incarnation of the HANDEL Nuclear Attack Warning equipment known as Wire Broadcast System WB1400. It replaced both the Verbal Warning WB400 and Siren Control WB600, in areas with a flood warning system it also replaced the WB601.

This first of two parts of this topic describes the broadcast of attack messages to the Carrier Control Points and the distribution to through the BT network of exchanges to the final exchange that feeds the customers receivers. Part two, covers the distribution to customers and customers speech and siren receivers.

National Attack Warning Centre

ADOC Control Unit

The main source of the National Nuclear Attack Warning would be Air Defence Operations Centre ( ADOC ) at Strike Command in RAF High Wycombe with a back up at the Preston U.K.W.M.O. Sector Headquarters, located at Langley Lane, Goosnargh, Lancs. This table mounted unit would be used to issue the message to the 250 Carrier Control Points (CCP).


Carrier Control Point - WB1400 Era

The United Kingdom is divided into 250 Warning Districts each served by a Carrier Control Points (CCP) installed in a Major Police Station in the district. Each CCP controlled the operation of Air Attack and Flood warning sirens and the broadcast of fallout messages within its local area.

Block Schematic of Connections to a CCP

The block schematic diagram shows how two private circuits from the telephone exchange carry the speaking clock in one direction and the 72kHz carrier in the other. In the previous topic we read how the speaking clock circuits would be used to distribute the attack warning broadcasts. These duplicated private circuits take different routes to avoid a damaged cable isolating the CCP at the police station. At the exchange the two incoming carriers are monitored and one selected for distribution.

A third private circuit is for bothway communication with the UKWMO Group HQ. The UKWMO is responsible for issuing fallout warning messages and an all clear when the radiation has fallen to a safe level.

The small WB1400 control unit 21½"W x 11½"D x 17"H shown below performs the same function as much two larger WB400 control units in the police office and two steel cabinets, each 1ft 10in wide x 1ft 2in deep x 6ft high in the police station apparatus room containing all the logic and signal generation equipment.

Carrier Control Point
Roll Mouse over photo

Roll your mouse over the photograph for a description of the parts of the CCP.

Each of the three handsets terminates a pair of wires from the Control Point Exchange (CPE). The two Red handsets are designated "X Path" and "Y Path" and have associated Red "Lift Handset" lamps and alarm sounder. Providing there are no line faults both handset alarms sound in response to a broadcast message from Strike Command, lifting either will stop both alarms. The Red handsets can only listen to broadcasts as there is no return speech channel to the ADOC.

CCP Switch Panel Closeup

Click to See what is underneath the grill.

The Black "Group" handset is for two way communication with the UKWMO Group Headquarters for the warning district(s) served by this CCP. It has a white alarm lamp "Group Tele" and alarm sounder indicating when the 'Warning Switchboard' at U.K.W.M.O. Group calls. To initiate a call to the Warning Switchboard, the alarm lamp cover that serves as a pushbutton is pressed, the alarm sounds for the duration of the press.

The same two pairs of wires, the 'X' and 'Y' paths, used to bring the national warning to the Red handsets also return two separate feeds of the 72kHz carrier signal back to the Control Point Exchange (CPE). The carrier is modulated by either Police Officers spoken messages or siren control signal. Mains fail alarms are signalled to the CPE over the 'X' and 'Y' path wires too.

This close up shows the control switches on the CCP. The siren can only be activated when the "MASTER" locked rotary switch, located on the bottom right, is turned through 90° clockwise to the ON position. Verbal warning messages may be sent without the master switch being activated.

The two right hand keys are pushed upwards to initiate their respective siren activation "ATTACK warning" or All "CLEAR" sequence. The "CANCEL" key stops activation sequence before it has run its full course. The siren control signal which consists of a sequence known as G and S tones can be heard through the grill above the keys. The sequences are described in the Power Siren Control Topic which follows later.

The same two keys pushed in a downward direction initiate a spoken broadcast to the warning receivers. The rotary switch under these keys allows either the "SELECT" group of receivers (Those used in ROC & UKWMO peacetime exercises) or "ALL" for every receiver (Wartime and Police quarterly tests) to hear the message.

There is a difference between the terminology used on the CCP panel and the ROC "Standard Operating Procedure, Annex P" which refers to the four or eight "W" tones as the 'Call' signal. The CCP 'Call' signal of rapid pips is called the 'Alert' signal in the ROC operating procedure. They do however agree on the wailing 'Alarm' signal.

During periods when the CCP is not being used it modulates the carrier with a soft beeping 'Monitor Tone'. This tone can be heard if the warning point presses the test button on the carrier receiver's loudspeaker. It purpose is to give confidence the receiver is working properly. It may also be heard for a short time after the end of a spoken message, before the receiver speak turns off.


Demonstration of WB1400 signals
The sequence below demonstrates both the control signals and the tones and messages passed to users. The column headings indicate the two type of receiver owner and first column indicated what would be heard by any user with the test button permanently operated.
Any Receiver with the Test button operated UKWMO Users
Public Warning Points
[Confidence Tone] tick-tick-tick Nothing Please single click the link below to hear the test message (50 Seconds duration). Users on dial-up will have to wait a few seconds whilst it downloads.

WB1400 Demonstration
(147 KiloBytes)
To Replay this message - Click the media player Play button again.
[Enable "SELECT" Signal] four rapid soft pips
[Call Signal] loud beeps
"This is a test message for Royal Observer Corps personnel only."
[Confidence Tone] tick-tick-tick Nothing
[Enable "ALL" Signal] eight rapid soft pips
[CALL Signal] loud beeps
"This is a routine test message for all users, you will now hear a demonstration of the alarm signal."
[ALARM Signal] loud pips
"Test Complete - Thank you."
[Confidence Tone] tick-tick-tick




Carrier Control Point : Duplicated Control Units for Security

C.C.P. Installation

Two CCP control units in two separate locations are provided for security against equipment failure and damage. The ''Working' unit was located at the secondary location, normally an office environment. The 'Standby' control unit would be plugged in at the primary location, typically an equipment room or secure basement accommodation. The user instructions describe what to do under fault conditions. The cables between the secondary and primary locations are called the 'House Wiring' it is connected to the flexible lead exiting the bottom of the 'Terminating Unit WB1400'

Extract from User Instructions

What to do if the normal control unit fails to indicate a confidence tick on both meters.

The 'Working' equipment is normally situated at the secondary operating location. Connect the equipment to the primary operating location 'Working' socket in place of the house wiring. If it then operates correctly the fault is in the house wiring and the equipment should be left operating at the primary location.

If the equipment still fails to operate connect the 'Standby' equipment to the 'Working' socket at the primary location. This equipment should then operate correctly.

Reconnect the house wiring to the 'Working' socket and install the 'Standby' equipment in the secondary operating position. It is important to inform British Telecom Fault Control if this action is taken.

Primary Location: Changeover Panel

Terminating Unit WB1400

Click to See Inside

The Terminating Unit WB1400 is the hub of the system in the Police Station. Internally there are two power units which should be fed from different mains supplies to guard against a ringmain fuse blowing. Connection strips terminate the external wiring to the building's Main Distribution Frame (MDF) carrying the two HANDEL circuits and the UKWMO Group HQ circuit back to the exchange. Next to the power units are six test links (four red for HANDEL and two black for ROC) intercepting these circuits allowing BT to setup and test the CCP. Other connection strips terminate the internal cables to the Terminating Unit WB1401 at the secondary location and the 100 hour standby battery.

The flexible hose emerging from the bottom of the unit has a plug that is normally connected to the 'Working' socket. The reserve control unit's flexible lead is normally plugged into the 'Standby' socket. This may be changed around to isolate faults and maintain a working CCP.

Timings and Frequencies of Signals Generated by the CCP

The purpose of the various control signals generated by the CCP has been described earlier on this page. While the frequencies used and timing of these signals is of little interest to the casual reader of these pages, owners of WB1400 receivers may be interested in this list extracted from the Telecommunication Instructions. E9 E3103.


Police Routine Functional Test

The police carried out a routine test of carrier receivers at 3 month intervals. The test was performed at 0900, 1500 and 2000 and repeated a total of five times at one minute intervals, consisting of a short test of both the 'Call' and 'Warning' signal and a spoken message using a codeword the receiver owner wrote on the test form they returned to the police.

Tunbridge Wells Carrier Control Point

I am most grateful for the feedback received from Nick Ashdown in March 2012 for an actual recording of a WB1400 test broadcast. I have reproduced an extract from Nick's email below. I find it incredible that two people have been kind enough to send me recordings of the same CCP but made decades apart.

I was recently going through old cassette tapes and found the attached recording of a routine test from Tunbridge Wells CCP on our WB1400 recorded on the 29th of July 1987. I thought it would be a good comparison to the WB400 (we used to have one of these before it was swapped to the 1400) recording you have also from Tunbridge Wells.

I made the recording as we planned to ask for its removal and wanted to have something to remind us of the little box next to the phone by the front door. Very few people in the village new of its existence, when people visited, if they asked we just said "it's something to do with the telephone". We also had a siren in its create which we also tested once a year or so, not at full speed as we did not wish to alarm the villagers.

Recording of a Routine Test Broadcast made 29/07/1987
[Confidence Tone] tick-tick-tick
[Call Signal] rapid pips
This is the Tunbridge Wells Carrier Control Point making a routine test broadcast.
You are now to hear a short test Warning Signal.
[Alarm Signal] wow-wow
Now please write the codeword Sunderland on your routine test report card.
Complete the remainder of the details and post.
Remember to switch off your loudspeaker, thank you.
[Confidence Tone] tick-tick-tick
Please click the link below to hear the broadcast (71 Seconds duration). Users on dial-up will have to wait a few seconds whilst it downloads.

WB1400 Test Message . M P 3
(212 Kb)
To Replay this message - Click the media player Play button again.
The WB400 for Comparison
This is a WB400 test broadcast also made by the Tunbridge Wells CCP. This recording was made circa 1966, 21 years before the one featured above. Note the wording is very similar.

A transcription of this message appears on the previous page. If you haven't already visited that page, afterwards, please use the tabs at the top of this page to look at the WB400&600 description.
Please click the link below to hear the broadcast (50 Seconds duration). Users on dial-up will have to wait a few seconds whilst it downloads.

WB400 Test Message . M P 3
(147 Kb)
To Replay this message - Click the media player Play button again.

Control Point Exchange WB1400 Era

I don't have a photograph of the Control Point Exchange (CPE) equipment, but it is a taller version of the cabinet shown below in the distribution section. The equipment cabinet in the CPE receives two feeds from different Speaking Clock distribution rings, shown as 'Spkg Clock' circuits 1 and 2 in the diagram. In an attack situation, messages from Strike Command are broadcast in place of the time signal.

CPE Block Schematic

The CPE consists of one control shelf and at least one distribution shelf. The thick double arrow lines represent the external lines to the Carrier Control Point (CCP). The 3 pairs of wires to the CCP leave on the left hand side. The X and Y paths are placed in different cables for security. Audio from the HANDEL interface goes towards the CCP. The 72kHz modulated carrier is received from the CCP.

The line between the CCP and the UKWMO Group HQ is routed via a signalling converter (Unit WB1400/10A) when Group calls the CCP, the balanced battery signal from Group is converted to 25Hz ringing towards the CCP. The CCP calls Group by placing an earth on its B-wire only, the converter sends balanced battery to call Group Headquarters. Whereas the HANDEL circuits are unidirectional, the line to the Group works bothways for speech and signalling.

Each HANDEL interface (Unit WB1400/1B) amplifies the audio from Strike Command in the direction of the CCP. It detects a 1200Hz plus 1440Hz P+Q signal lasting for more than 1 second sent immediately before the warning message and converts this into a 180Hz signal of 711mS duration to alert the CCP. A filter blocks the carrier coming back from the CCP over the X and Y paths from the audio amplifier.

The carrier from the CCP should be received along both the X and Y paths. A preamplifier (Unit WB1400/2B) in each path monitors the carrier, if it fails, a signal is passed to the changeover unit (Unit WB1400/7B). The changeover unit control signal allows only one of the pair of pre-amplifiers to turn its output on. Whichever output is enabled feeds the carrier to the distribution shelf in the cabinet. Should one path fail the other path is selected. A manual changeover button is also provided.


Carrier Distribution between Exchanges

District Distribution

All dependent exchanges only had a single feed, as now, unlike the previous system the duplicated X and Y carrier paths only extended as far as the CPE. This was possible as the likelihood of faults was reduced as the majority of rural exchanges were fed by underground rather than overhead cable by the time WB1400 was introduced. Security of supply was considerably improved now a loss of carrier at an exchange raised a maintenance alarm.


Carrier Distribution to Warning Points

Cabinet Front

These photographs (taken at the Avoncroft Museum, Bromsgrove 15/07/04) show how the Equipment Carrier WB400A and Box Battery WB400A, formerly used for the WB400 system was modified to house the WB1400 distribution equipment. The cabinet is part of the exhibit of small rural dependent exchange 'UAX13' at the museum.

Cabinet Rear

The main cabinet is 1'-10½" wide, 1'-0½" deep, its height above battery box 2'-8". The Battery Box is 1'-10½" wide, 1'-2" deep, 1'-11" high. Both are made of heavy gauge steel and are connected to the Main Distribution Frame via a conduit for the cables.

WB1400 Distribution Shelf

Click to Zoom

Removing the screws and lifting off the front cover reveals an Equipment Carrier WB1402, Diag. WB29604; a shelf of slide in units which may be dropped forward to give access to the cards. In the enlarged view a strip indicating which unit fits in the position can be seen along the bottom of the shelf. For example 4B is a Unit WB1400/4B

The incoming carrier signal from the previous exchange enters the shelf via the Filter Unit which sends the signal to the pre-amplifier a Unit WB1400/2B, The output from the pre-amplifier is connected to the inputs of 3 x Unit WB1400/4B Distribution units. Each distribution unit further amplifies the carrier and provides 5 outputs. Any of the 15 outputs can be connected to outgoing junctions to feed dependent exchanges or used to supply customers lines to warning points.

Should the incoming carrier signal fail, an exchange fault alarm is raised via the Unit WB1400/8B which also handles the power supply to the shelf. Power is normally obtained from the telephone exchange 50 volt supply, should this fail, the reserve battery in a box under the cabinet will take over.

Shelf Schematic

The shelf can be fitted with 5 x Unit WB1400/5A. Each can supply up to two customers lines with the trickle charge for the Speech Receiver. The unit also detects the signal returned from the Siren Signalling Receiver in response to the automatic test signal sent by the CCP. If the trickle charge fails (Line broken) or the test signal is not returned from a siren control unit a telephone exchange maintenance alarm is raised.

If the Unit WB1400/5A fitted in the last shelf position is removed and replaced by a Unit WB1400/6A, it produces two demodulated audio feeds instead of 2 trickle charge feeds. The audio feed is only used in a limited set of circumstances when it is not possible to serve a dependant exchange by carrier. This could occur if the line loss at carrier frequency exceeds the maximum permitted or the exchange is connected by a radio link. At the dependant exchange the Unit WB1400/2B is replaced by a WB1400/3A which modulates a locally generated 72kHz carrier with the incoming audio signal.