|Bell Set 50B - Low impedance bell ringer mounted on a 746 baseplate.
Bell Set 50C - as above but with high impedance bell ringer.
Set 50E - Plug-ended High Impedance Bell Set with 3 Metre cord for use on PST, supersedes
Bell Sets 50B & 50C for new supply and maintenance replacement, available on sale or
The bell is line powered.
Originally made by Denis Ferranti Ltd, now made by Gemini
Bell Set 50E - S/1000/23/K/501724.
Modifications which have not received appropriate approval must not be carried out as to
do so would invalidate approval making connection unlawful. Bell Set 50E or 'Extension'
line cord may be shortened without breaching approval.
Bell 50E - for interior wall mounted use, supplied with plug ended cord for use with any
phone socket. Measures approx. 145mm x 145mm x 57mm, weight 470 grams. Comes with 2 wood
screws, wallplugs and template for positioning screws. REN 1.
Phone sockets provided for plug-ended ringing devices should have all conductors
terminated in accordance with standard cabling practice so that they may be used for
connection of other apparatus if required. Where for engineering reasons (e.g. PBX Night
Bell) or at customer request the ringer must not be unplugged, the plug may be secured by
fitting a 'bar locking'.
Exceptionally, where a phone socket is provided for an extension bell / Ringer at a
payphone, terminations may be made to phone socket terminals 3 & 5 only to prevent
unauthorised use by telephones.
The Line cord of Bell Set 50E may be cleated in place using cleats wiring 4C and if
necessary (with customer agreement) be shortened (to a minimum length of 300mm) where bell
/ tone caller is to be fitted adjacent to phone socket.
Bell Set 50B (Low Impedance bell set for use with hard wired, series connected extension
bell arrangements) are no longer available centrally. On BT faulty Bell Sets 50B should be
maintenance replaced by Bell 50E and system converted to PST. Existing serviceable Bells
Sets 50B and 50C (pictured to the right) may be used for internal shifts.
Where the addition of bells tone or callers results in ringing difficulties because the
system is approaching or exceeding REN limitations or capacity of PBX Night bell port, it
may be necessary to fit a 'Converter Ringing 15' to boost ringing output.
|Bell No. 50C internal view
||Bell No. 50C external view
Taken from BT instructions circa 1989
Click here for the difference between a Bell and a