|The original part numbers for the Muraphone was three digit numbers (GEC
Magazine) but in 1946 the phones were re-numbered ST 23xx, ST 24xx, ST 25xx and ST 26xx series
and again in1955 GEC decided to renumber all their telephones with the prefix
TEL. Please see the table below and also follow the link called "click here for
Click here for general information on the Muraphone
Click here for the Muraphone K - updated Muraphone
with new style handset and circuitry
Click here for information on how to convert your
Muraphone to Plug and Socket
Click here for the Muraphone circuit diagram
The picture shown to the right is the earlier Muraphone, which easily identifiable by the spittoon
mouthpiece. The later version, known as the Muraphone
K, has the modern curved handset, without the spittoon mouthpiece.
A wall-mounting telephone for use with all automatic or C.B. manual systems.
Designed in two slightly-different types, one for the usual public service
systems and the other for hotels, service flats and passenger vessels.
The case is a plastic moulding, in either black or a selected colour. It is
shaped to form a cradle for the receiver and a housing for the transmitter, so
that the handset is securely held in a vertical position. The front surface is
the correct width to accommodate a dial, and the circular motif is repeated at
the sides of the moulding by concentric segments. These are provided with
sound-outlet apertures for the bell or buzzer with which the Muraphone may be
The cradle switch is extremely positive in action, and is operated by a lever
on which the receiver rests when the handset is in position. Rollers, attached
to the switch lever, actuate the switch springs. These are provided with twin
contacts, and the leverage obtainable allows contact pressures to be greater
than in plunger-type cradle-switches.
The G.E.C. dial is the British Post Office standard, with stainless steel
fingerplate. It is fixed to a special support, so that the case can be removed
entirely. The C.B. Muraphone for public systems is convertible to automatic
working by the removal of the dial dummy, replacement by a dial, and connexion
of a dial cord.
The terminal strip, mounted at the lower end of the unit, terminates line
wires, handset cord and dial cord on screw terminals, which are separated by
moulded insulators to prevent surface leakage. A tight-fitting rubber bush
anchors the handset cord to the terminal strip. This arrangement relieves the
conductors of the strain from a direct pull, seals the point of entry, and
allows the cord maximum flexibility without the possibility of frayed braiding.
For Ships, Hotels, Flats, etc.
For the model specially designed for ships, hotels and flats the subdued
note of the buzzer is generally preferred to the louder ring of the bell, and
plunger-type terminals replace the screw-type for line wires. Line wiring can be
concealed in the decorations and terminated on a small connexion block, which is
provided with sockets to take the plunger terminals when the Muraphone is fixed
to the wall. This type of Muraphone can thus be plugged in to existing wiring as
Because the systems for which it is designed are not likely to change from
manual to automatic operation, the C.B. version is not designed to allow the
quick fitting of a dial.
The B.P.O. standard inset-type transmitter and receiver are included in a
high-efficiency speech circuit which gives the intelligibility that results from
the maximum suppression of sidetone.
A spark-quench circuit protects the dial impulse springs.
If required, a suppression circuit can be included to prevent interference
with nearby radio receivers during dialling.
The tropical Muraphone incorporates special features which are the result of
- A shunt is connected across the transmitter to minimise the minute arcing
that tends to occur at the granules and electrodes as the cradle switch
operates the accelerated tendency towards frying often shown by transmitters
in the tropics is thereby offset. The effect of any increase in transmitter
resistance upon line circuit conditions is also minimised by the shunt. The
loss in volume efficiency is very small and is partly cancelled by reduction
of sidetone, the net result being a difference of only 1 db.
- Apertures in the case are covered with fine wire gauze to prevent the
ingress of insects.
- Metal parts and all wiring are specially finished and treated to resist
the effects of high-humidity atmospheres.
- Cradle-switch springs are covered with varnish to maintain insulation
- Flexible conductors are V.I.R. covered and braided overall.
- All coils are specially treated to render them impervious to damp, heat,
and sudden variations of temperature.
- For very dusty atmospheres, a bakelite cover can be fitted to the back of
the dial, giving complete enclosure of the mechanism.
The standard colour is Black, but enquiries are invited for the telephone in
Ivory, Jade Green or Chinese Red, with cords finished to match.
Connexion Block for line wiring for Muraphones with plunger terminals - Cat.
No. CBI 101.
Height, 9.3” (25 cms)
Width, 5.3” (14 cms)
Depth (over handset), 5.75” (15 cms)
Average of all models, 4.25 lbs. (l.9 kgs.)
Taken from the Catalogue Leaflet No. STL.7
Pre 1955 Catalogue Numbers
CATALOGUE NUMBER CONVERSION TABLE
|Obsolete Part Number
||Revised Part Number
||C.B. Bell, Screw Terminals, Std
||C.B. Buzzer, Screw Terminals, Std
||C.B. Bell, Screw Terminals, Tropical
||C.B. Ships, Bell, Plunger Terminals, Tropical
||C.B. Buzzer, Screw Terminals, Tropical
||C.B. Ships, Buzzer, Plunger Terminals, Tropical
||C.B. Bell, Plunger Terminals, Tropical
||C.B. Buzzer, Plunger Terminals, Tropical
||Automatic, Bell, Screw Terminals, Std
||Automatic, Buzzer, Screw Terminals, Std
||Automatic, Bell, Screw Terminals, Tropical
||Automatic, Bell, Plunger Terminals, Tropical
||Automatic, Buzzer, Screw Terminals, Tropical
||Automatic, Buzzer, Plunger Terminals, Tropical
ADDITIONAL INFORMATION AND PICTURES
These are pictures are of the original Muraphone - easily
identified by the spittoon mouthpiece
|ST2301 - CB version
||ST2502 - Auto version
|ST2510 Internal view
||ST2510 External view
|Early picture of the terminal block
connector model - note no screw terminals for L1, L2 or E, as the block
connects to the rear
||Same telephone shown to the left, but with
the dial removed to expose all components that are mounted on the base plate
Front view. The grey cord and terminal block were
not originally supllied
Front view showing the earlier spittoon style handset
View of base plate showing original feet
The wall fixing screws went through the centre of the feet
In the picture above, the feet are
fixed by screws - it is thought that the feet on this phone have been