Solar Calendar Time Switch


Hortsmann Type V solar calendar time switch


SKU: 1995/002 Categories: ,


Hortsmann Type V solar calendar time switch in a metal case manufactured for latitude 56 degrees: an electro-mechanical time switch self-adjusting to sunrise and sunset times (GMT). There is an advance and retard mechanism which allows the switch to operate at preset times before or after sunset or sunrise.

A device like this was used in nearly every lamp column in Edinburgh up until 1975 when they began to be replaced by photoelectric cells: they are still used today (November 1994) in a small number of older columns. They were generally regarded as having a high degree of accuracy but there were cost and practical implications of their continuing use: (1) every switch needed to be reset following any power cuts of significant duration, (2) watchmakers were permanently employed to maintain and repair the mechanism. These mechanical time switches have now been superseded by electronic switches. They are sought after quite avidly by some collectors.

Additional information

Acquisition Number


Item Type

Short Description

Hortsmann solar calendar time switch

Manufactured by

Date of Manufacture

c. 1970


Plastic cover

Supporting Items

Booklet entitled "Street Lighting Times Table" issued by City of Edinburgh Lighting and Cleansing Department

Makers Number




Dimensions (mm)

130 x 130 x 90


Date Donated

November 1995


Bakelite and metal



Display Location