Tannoys/PA systems on trains

[StephenHunter]

When did in-train (as opposed to in-station) tannoys start being used on BR?

 

[30907]

Recent thread here:
https://www.railforums.co.uk/threads/history-of-on-train-pa-systems-in-the-uk.210853/#post-4846677

 

[hexagon789]

When did in-train (as opposed to in-station) tannoys start being used on BR?

The Blue Pullmans certainly had a PA

The Mk2D coaches were I believe the first 'normal' vehicles so-equipped, they even had an automatic tape cassette system which played pre-recorded announcements deriving location from counting axle rotation.

 

[copea]

The “Audio Navigator” was fitted to several BG’s on West Coast main line in the 1970 which made automated announcements using the RCH lighting jumpers between vehicles from Mk2D onwards. It counted axle revolutions between stations. However, when trains were diverted it upset the system, particularly on Sundays, so soon fell into disuse.

 

[hexagon789]

The “Audio Navigator” was fitted to several BG’s on West Coast main line in the 1970 which made automated announcements using the RCH lighting jumpers between vehicles from Mk2D onwards. It counted axle revolutions between stations. However, when trains were diverted it upset the system, particularly on Sundays, so soon fell into disuse.

It also didn't compensate for wheel wear so unless periodically adjusted went out of kilter soon enough.

Modern GPS based systems can still get it wrong too though!