Petone - The Control Machine

In the 1950s when the Petone panel was commissioned personal computers were science fiction. The panel on the first floor of Petone Box is the equivalent of a Graphical User Interface (GUI), controlling the relay logic located on the ground floor and also in some field locations.

The signalman operates the points and signals directly, rather than setting the route and allowing software to make the required changes. In a modern electronic signalling system the panel would be replaced by a window in a PC - boring!!!!!.

Signal lever

The Petone Panel

Petone Panel



A down train is at Ava and another train is at Melling.

Petone once controlled the Lower Hutt yard.

There are differences between the tracks shown on the diagram and on the handsketch for the junction area.

Note the quick and simple methods used to make changes to the diagram. The yellow paper hides the now lifted Fletcher siding.



47 points are in the reverse position and are free because no signal has been cleared over them, there are no track circuits occupied and 48 points are normal.

Signal 77 has been cleared for a train on the down main, locking 48 points (the crossover) normal. When a train passes 77 signal the indication will change from Green to Red. If the Down Main is switched-in the indicator light will flash, meaning that the lever must be put to stop. If another train is to be signalled on the down the light is allowed to flash until the train has cleared the overlap; the lever is then restroked.

Switch Layout and Signal/Point Numbering

Petone lever layout

The numbering of the points and signals is based on the position of the switch on the panel. This explains why signal 14 is followed by 17 but signal 11 was followed by 13.


Notifying Trains.  Originally information about trains was passed from signalbox to signalbox by bell codes. When a signalbox switched-in the box was connected to the bell and phone circuits.The bells were out of use by ??.

2007 Procedure.  In 2007 the signalman at Petone worked from a pre-printed train register. Extra trains, such as 634, staff training EMUs and test MUs are notified by phone.

Bell Codes.  The following codes are from the 1965 Rule Book:

Express Passenger Train

2 pause 2

Express goods; breakdown train; relief engine

3 pause 1


4 consectively

Passenger train

2 pause 3

Empty carriage train

2 pause 2 pause 1

Mixed train; with car goods

5 consecutively

Goods train

6 consecutively

Light engine; light engines coupled

2 pause 2 pause 2

Work train

3 pause 3

Cancel bell signal

3 pause 4

Speak on telephone



(Above)  This indicator reminded the signalman which box the bell circuit was connected to. The indicator did not perform any switching function. The slides were moved to the left to display in turn Woburn, Taita, Trentham & Upper Hutt.
(Below) The plunger used to bell A-Box.

Wellington Bell

Switch In & Out and Indications Check

Up & Down Mains.  The Up and Down Mains can be switched in and out independantly. When a main is switched-out the running signals display illuminated A-lights and operate automatically.

Switching Out.  All points levers must be in the normal position, as must be the levers for the up and down main running signals. Signal 78 on the branch must be at stop.

Switching In.   The levers can be in any position when switching in. The signals will go to the state specified by the lever - care must be taken not to put a signal to stop in front of a train.

Traditional Switch-in practice.  When the signalman was on duty both mains were kept switched-in - the bell and phone circuits bypassed the box when switched-out. (My assumption about procedures).

2007 Switch-in Practice.  The bells are not used and the phones are permanently connected so the up and down mains are switched in and out as required. Typically the up is switched-in from about 0630 until 0935, then as required. The down is normally switched out, only being switched-in to get a down Melling off the branch.

How the Indications Check lever was originally used.  This is a guess on my part. The signalman used the switch-in and switch-out levers and did not operate the Indications Check lever, which was kept in the anti-clockwise position. If someone entered the box when it was switched-out they could turn the Indications Check lever clockwise to turn power on and determine the position of trains. Switching-in would have interrupted the bell and telephone circuits between the adjacent boxes.

How the Indications Check lever is used in 2007.  On commencing duty the Indications Check lever is turned clockwise, turning on power to the panel. The switch-in/out levers are kept in the Out position until it is necessarty to switch in. Before locking up the signalman switches both mains out. The Indication Check switch is then turned anti-clockwise, which removes power from the panel. The power remains on if either main is switched-in. This is a convenient check that the station is switched-out.

Switch out


When the Down Main is switched in a buzzer sounds when the approach track circuit is occupied. The same applies on the up main.

Up Buzzer Cancel

Last Updated: Wed Feb 29 17:25:49 NZDT 2012

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