The Racal-Dana Frequency Standard Distribution System 9478 provides a reliable and convenient means of generating and distributing up to nine standard frequency signals, all phase locked to a single frequency standard. Where more than nine independent outputs are required, two or more systems may be cascaded. FREQUENCY STANDARD The frequency standard used may be internally mounted. A choice of two crystal oscillators from the Racal-Dana range is offered. The specifications of these oscillators are given in Section 1. Alternatively an external master oscillator or atomic frequency standard may be used. External frequency standards having outputs at 1 MHz, 2 MHz, 2.5 MHz, 5 MHz or 10 MHz are all suitable for use with the 9478. Systems fitted with an internal frequency standard will automatically lock to the input from an external standard when such an input is present. SYSTEM OUTPUTS The nine BNC output sockets are mounted on the rear panel. Each is fed from' an individual driver amplifier and provides a level of 1 V r.m.s. into 50 ft. Internal coaxial links, which may easily be reset by the user, allow the frequency at any output to be set to 1 MHz, 5 MHz, or 10 MHz. STATUS INDICATORS Each output channel is provided with an individual LED indicator. These are mounted on the front panel, and light when an output is present. In addition a TTL compatible, logic '1' alarm signal is given at a rear panel mounted connector if any output fails. Two further front panel LED indicators are provided. One lights when the system is in lock, and the other when an input from an external frequency standard is present. Both indicators are repeated, in the form of TTL compatible logic '1' levels, at a rear panel mounted connector.