Ground frame
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A ground frame is a small assembly of interlocked mechanical levers located beside a railway, usually at ground level. A ground frame does not normally require any form of shelter since it is usually operated by traincrew and not permanently staffed. A ground frame is typically used to control the points giving access to an infrequently used siding where the expense of providing control from a remote signal box cannot be justified. In some situations, signals may be worked from a ground frame.
[edit] Method of Release
In most cases, a ground frame has to be released from a signal box before it can be used. Typical methods of release include:
- Mechanical midway release.
- Release by key (e.g. Annett's key).
- Release by single line token.
- Electrical release.
The release cannot be restored until all the levers in the ground frame have been returned to their normal position.
[edit] Ground Switch Panels
The modern equivalent of a ground frame, with switches instead of levers, is called a Ground Switch Panel (GSP). Obviously, any points or signals worked from a ground switch panel must be electrically operated.
