tension. The high voltage of several hundred kilovolts on the topload wires during transmission requires long strings of insulators where the wires are attached to the towers. It is a NATO facility, controlled from Northwood Headquarters along with three other VLF transmitters in Norway, Germany and Italy. In accordance with the procedure for NATO projects, the project was the subject of a competition among the organisation's member countries. The British Post Office, acting as technical adviser and agent of the Ministry of Defence, chose the site, negotiated the contract and supervised the work, with the assistance of the Ministry of Public Building and Works. The contract was placed on 26 October 1961 with Continental Electronics Systems Incorporated of Dallas, Texas. This firm had already built a similar but much larger station in Maine, USA. Work began in 1962 and the station was accepted on behalf of the MoD in November 1964. Originally, the station was designed to radiate a single telegraph channel at up to 45.5 baud and at powers ranging from 50 kW at 16 kHz to 100 kW at 20 kHz. The carrier frequency was to be stable to one part in 108 over a month. Subsequently, the data rate was increased to 50 baud and the carrier stability improved. LF transmitter: National Physical Laboratory time signal The National Physical Laboratory (NPL) has installed three atomic clocks at Anthorn, and on 27 February 2007 Britain’s national time signal transmissions, retaining their original call sign of MSF, were transferred there on a trial basis, moving formally on 1 April 2007. The signals were previously transmitted from a transmitter at Rugby, administered by BT. The data transmitted includes time and date information which can be decoded using readily available software, and the signals are transmitted at an accurate frequency of 60 kHz to provide a national frequency standard.. The transmitting aerial uses an auxiliary mast adjacent to the VLF array. Monitoring and logging of the clocks and control of the transmissions is by Internet link from the NPL offices at Teddington, using comparison with GPS signals at both locations. Signal monitoring is by radio. To ensure accuracy, dynamic adjustment of the aerial according to local conditions (such as wind distortion) is controlled from computers on site. The effective radiated power is 17 kW. LORAN The general lighthouse authorities for Britain and Ireland have contracted VT Communications to develop eLORAN (enhanced