Woods Keys

The Woods key provides a low capital cost but high operating cost form of interlocking. The key, which performs the same function as the Annett key used in Australia and the UK, was used only in New Zealand.

In 2004 it is possible that the only extant Woods keys are the two in daily use at Masterton in the Wairarapa. The reason that the Masterton keys have survived is probably the diesel hauled commuter trains that operate seven days a week.

On this page I have documented the Masterton Woods keys before it is too late.

The current Masterton A key is a replacement.

Woods Keys

What is a Woods key? The principle is that a signal and its associated facing points are unlocked by a single key. When the signal lever is reversed the key is impounded in the lock, preventing the points being reversed. The reverse also applies - unlock the points and the signal cannot be cleared. In effect the key and associated locks perform an "OR" function. This provides a low-capital but high-operating-cost form of interlocking. The keys and locks were named after S P Woods of McKenzie and Holland.

Annett Keys The Woods key is similar to the Annett key used in Australia and the UK.

Pattern There were five patterns of Woods key, labelled "A" to "F". The position of a locking nib determined the key type. A faceplate on the lock ensured that only the correct key could be used.

Reference This information is from Semaphore To CTC by R W Heine.

From 1988 Rule Book.

103. Use and Custody of Woods Points Keys - (a) Woods points keys, when not in use, must be kept in the place appointed for their safe custody.

(b) Before using a Woods points key to operate signal levers a Signalman must satisfy himself that all other points keys are in their appointed place or, when any key is in use, that the points to which it applies are correctly set and secured for the passage of trains.

(c) When a Woods points key has been been removed from its appointed place the Officer in Charge must see that it is replaced immediately it is no longer required.

Lock & Key Patterns

Signal Lever Locks

"B" lock on the Masterton Down Home lever (left) and "A" lock on the Up Home lever (right). There were a total of five patterns (A to E) although only the "A" and "B" locks are in use at Masterton.

Woods Keys

The Masterton "B" key is on the left and the "A" key on the right. Note that the "B" key appears to have been converted from an "A" key.


Points Lever Locked

8 main to loop points at the north end are locked. The smaller slot is at 180 degrees to the larger slot so a "B" key is required to unlock the points.

There are two sector plates, one for the catch handle and the other for the lock. Turning the key lifts a dog.

I am not sure how the key is impounded because there is a slot in the sector plate in the reverse position. This allow the key to be rotated. Also not sure of correct terminology.

Points Lever Unlocked

The "B" key has been inserted in the lock on 8 points at the north end of the Masterton yard. The points are unlocked, although they have not been reversed.

Points Lever Unlocked

8 main to loop points at north end of the Masterton yard. The "B" key is in the lock and the points have been unlocked. The locking dog has been raised from the notch on the quadrant, so unlocking the points.

When the points are reversed the key will be impounded in the lock, so preventing the reversal of the 2 Down Home signal or of the down main to loop points or the Gas Works points which also face down.

Signal Frame

The Woods keys are in the Masterton signal frame so the associated facing points cannot be reversed. The Up Home (right) has been pulled off, impounding the key. Interlocking between Up and Down Home levers prevents the Down Home also being pulled off.

The white levers are out of use and were for the semaphore Distants. The latter were replaced with two-position colour light signals sometime between 1959 and 1971.

Sleeper Lock

The keyhole on the A6A sleeper lock indicates that an "A" key is required.

Last Updated: Tuesday, July 26, 2005

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