In 1963, the original device was replaced by more modern recording technology using a magnetic drum, similar to the Audichron technology used in the United States. The company that manufactured the rotating magnetic drum part of the Speaking Clock was Roberts & Armstrong (Engineers) Ltd of North Wembley. They took on the licence from the British Post Office to manufacture complete clocks for the telecommunications authorities of Denmark, Sweden and the Republic of Ireland, and a third (spare) clock for the British Post Office. The latter was installed in Bow Street, London. The European clocks were modified for the 24-hour system by lengthening the drum and adding extra heads. Roberts & Armstrong subcontracted the electronic aspects to the Synchronome Company of Westbury. The clocks were designed to run non-stop for 20 years. This system gave way to the present digital system in 1984, which uses a built-in crystal oscillator and microprocessor logic control. The complete apparatus comprises solid-state microchips, occupies no more shelf space than a small suitcase and has no moving parts at all. The BT service is assured to be accurate to five-thousandths of a second.