GPO CANDLESTICK


Candlestick Construction

The GPO standard pillar table telephone, better known as the candlestick, first appeared in the 1907.  The GPO being a large organisation had inherited many telephones from other telephone companies and wanted a standardised design that was simple, pleasant to look at and adaptable.  The candlestick remained popular for many years because it could easily be carried about the room.  

The active components were big in those days so they were contained in a separate unit, the Bellset.  If a generator was required then another box containing a generator would be supplied.  The wall phones were of course much larger and could contain all the active components.

The telephone casing stands on a cast steel base plate (0.075in thick), which adds weight to give stability (1lb 10oz).  Set into the base plate is a rubber ring which protected surfaces from scratching.  The rubber ring is a ¼in square section with a bottom curved.  The base plate is fixed to the phone with a central screw.

The curved base and tubular shaft are two steel pressings.  The shaft screws onto the base.  The steel gives structural rigidity without raising the centre of gravity, preventing toppling.  The metalwork has a black finish which is stove enamelled.  The cable entry has an Ebonite grommet to prevent the cables from chaffing or making contact with the metalwork.

On top of the stem is the transmitter support.  This is a single brass piece, turned and machined to shape.  The transmitter support is hinged using a separate brass piece called the bracket transmitter.  The transmitter is fixed to this bracket and could be on many types.

Housed within the stem is a mild steel chassis which, at the top, is fixed to the transmitter support and at the bottom is a nut.  The chassis has the Switch hook arm, the switch hook contacts and the terminals fixed to it.  The chassis is offered into the stem and lowered.  Once the transmitter support locates on the top of the stem, the base plate is offered up and the single screw in the base plate locates in the nut on the chassis.

The switch hook design was new and this style became the BPO standard.  It was introduced because of the danger of external wiring making contact with mains and trolley bus cables.  Up to that point nearly all the switch hooks used the lever as a live contact, which meant the whole phone was live.  The new version was completely insulated by the use of Ebonite.  The mechanism also allowed the lever to be easily removed.

The switch hook lever is brass with a black oxidised finished.

The receiver was the BPO Standard Receiver, or Receiver, Bell No.1 and unlike some earlier receivers had no exposed connections.  The receiver casing is covered with a Pellolit or Ebonite coating, which were originally black, but generally disintegrated or turned brown through aging.  This coating was an additional insulation.  The earpiece was made of Ebonite with an indentation on the edge.  There was a worry that users may place and leave the receiver on the table surface instead of placing back on the hook switch.  If a telephone was found to be off hook then a howler was connected to the line and the indentation would allow the noise of a howler to be heard.

As the transmitter bracket had standardised fixings numerous transmitters could be mounted.  Originally the Solid Back transmitter with daffodil mouthpiece was used, but this was later replaced with a Bakelite housing containing a carbon granule inset transmitter.

A diagram was pasted on the internal side of the base plate and the model number, year of manufacturer and name of manufacturer was stamped on the uppermost part of the transmitter support.

With the introduction of the dial, circa 1924, the base was modified with a circular flange which accepted the BPO standard dial.  When a dial was not required a blank plate was fitted instead.

Although the BPO had different numbers for candlesticks the only differences between them was generally variations on the switch hook contact springs.

Cross section of the Candlestick body

 

 
 
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Last revised: July 25, 2021

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