GPO / POST OFFICE SERVICE
WB 600

The siren control part of the WB400 system was added a few years after the installation of the WB400 and was confusingly designated WB600 as both use the same carrier and share the distribution network. In the apparatus room, the second steel cabinet "Equipment Signalling WB400A" which housed the alarm circuitry to detect the P+Q tones for HANDEL had two spare shelves. Two siren sequence generators were retrofitted into these spare bottom shelves.

The GPO installed the line and terminating equipment, with the Home Office responsible for installing and maintaining the Siren and it's associated equipment.

TI A8J2058 - Installation at a Control Point

TI C3 J1154 - Subscribers Installation

TI C3 J1160 - Siren Control Point Installation

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