Carrier System WB1400

Introduction

The Early Warning System WB1400 was installed during the early 1980's to replace the rather dated WB400 / WB600. It retained the same carrier frequency and signalling tones but contained many additional features. It incorporated a speech broadcast system, air attack warning system and included provision for flood warning. Many of the operational problems were overcome by better design. The most obvious was the removal of the reliance on dry batteries. Compared with the earlier systems that were designed and built in the 1960 using Germanium transistors, the WB1400 is physically much smaller and designed to withstand EMP. The WB1400 ceased to be operational in the early 1990's when the Cold War came to an end and civil defence was scaled down. If you would like to compare the WB1400 with the older system, links are proved at the bottom of the page.

If you have WB1400 equipment in your premises and are searching the web to find out what it is and if it can be removed - the web site may be contacted (see Topic Index at the bottom of this page) for advice.

I stopped maintaining the Carrier Systems in 1981, so have never worked on the WB1400. The CCP photographs on this page were taken by John Griffiths replacing those taken on my visit to Hack Green Museum in April 2002. There is a working demonstration system there, a gift from BT, but sadly out of reach of visitors. Others pictures were taken in the Telephone exhibits at the Avoncroft Museum, Bromsgrove in July 2004.

Carrier Control Point

This is the control unit (Equipment Carrier WB1400) housed in the operational area of a police station. There was a second identical unit kept in reserve that may be deployed if the main unit fails. Anyone lucky enough to own one may be able to get it partly functioning. Details

This small control unit performs the same function as the two large control units plus two steel cabinets, each 1ft 2in deep x 1ft 10in wide x 6ft high in the police station apparatus room, which housed the signal generation and amplifying circuitry required by the WB400/600.

The Carrier Control Point (CCP) contains all the logic and signal generation systems on the printed wiring boards within the unit itself. The black handset is for communication to and from the ROC group HQ for the area this CCP serves. The two Red handsets are designated X and Y; receive broadcasts from Strike Command, they have associated alarm lights and buzzers which would be triggered before the spoken message. The CCP cannot talk back to Strike Command, but the handsets are used to broadcast local warning messages. Each handset is at the end of a pair of wires from the Carrier Control Exchange. The carrier signal modulated by the police officers voice or siren control signal is sent over these same wires back to the exchange. The wires are also used to signal if the reserve battery is being charged from the mains supply.

This close up shows the control switches on the CCP. The siren can only be activated when the 'MASTER' rotary locked switch located on the bottom right is turned to the on position. The verbal warning messages may be sent without this switch activated. The two right hand keys are pushed upwards to sound their respective siren activation 'ATTACK warning' or 'all CLEAR' the 'CANCEL' key stops the siren sequence before it has run its full course. The siren control signals which consist of a sequence known as G and S tones can be heard through the grill above the keys. They are described in the Power Siren Topic which follows later. The same two keys held operated in a downward direction causes the warning receivers to be turned on to hear an 'ALARM' or 'CALL' sound followed by the spoken message. Either of the red handsets may be used to announce the message when the 'SPEAK NOW' light illuminates at the end of the prefix sound. The rotary switch under these keys allows either the 'SELECT' group of receivers or 'ALL' the receivers to hear the message, by the use of two different 'W' signals. This is explained further in the Warning Point Topic. The modulation meters indicated to the operator the correct level for the spoken message. The needle should be within the thick black line. During periods when the CCP is not being used it generates a beeping confidence tone. You may listen to the confidence signal at the bottom of this page.

Carrier Control Exchange

I don't have a photograph of the Carrier Control Exchange (CCE) equipment, but it is a taller version of the cabinet shown below in the distribution section.

The CCE consists of one control shelf and at least one distribution shelves. The thick blue lines represent the external lines. The 3 pairs of wires to the CCP leave on the left hand side. The X and Y path are placed in different cables for security.

The line between the CCP and the ROC Group 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.

The HANDEL interface (Unit WB1400/1B) amplifies the audio from Strike Command in the direction of the CCP. It detects the P&Q signal sent before a warning message and converts it to a 180Hz signal to alert the CCP. It blocks the carrier coming back from the CCP over the X and Y paths from the audio equipment. You may listen to the P+Q signal at the bottom of this page.

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. Should one path fail, the other path is selected. A manual changeover button is also provided.

Distribution

The WB1400 used a similar method of distribution as the WB400, but the dual path only extended from the Control Point to the Exchange.

These photographs (taken at the Avoncroft Museum, Bromsgrove 15/07/04) show the Equipment Carrier WB400A and Box Battery WB400A, formerly used for the WB400 system and reused to house the WB1400 distribution equipment. This version was for a single path dependent exchange. Dimensions Equipment Carrier WB400A, 1-10½ wide, 1-0½ deep, height above battery box 2-8. Empty weight 115lb. Box Battery WB400A, 1-10½ wide, 1-2 deep, 1-11 high. Empty weight 40lb.
Taking off the screw on front cover reveals a shelf of slide in units which can 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	Normal Position	Click for an enlarged view

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, should the incoming signal fail a fault alarm is raised via the Unit WB1400/8B which also handles the power supply to the shelf. Power is normally obtained from the exchange 50 volt supply, should this fail, the reserve battery under the unit will take over. 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. The 15 outputs can be connected to outgoing junctions to dependent exchanges or customers lines to warning points as required.

The shelf can be fitted with 5 x Unit WB1400/5A these can supply up to 10 customers lines with the trickle charge for the Speech Receiver and they monitor the OK signal that is returned from the Siren Signalling Receivers 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 an alarm is raised. If one Unit WB1400/5A is removed and a Unit WB1400/6A fitted in the last shelf position, it produces two demodulated audio feeds in place of 2 trickle charge feeds.

For a customer with WB1400, their exchange equipment is routed via the trickle charge and monitor unit, then out to line. A carrier feed from the distribution amplifier is connected to the same line connections. A block within the monitor unit prevents the carrier being shunted by the customers exchange equipment.