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1959 - History of Ericsson - History of Ericsson

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Fig. 7<br />

Relay room FSR<br />

x 2484<br />

Trunk Equipment<br />

A block schematic <strong>of</strong> the trunk equipment is shown in fig. 6.<br />

Every trunk circuit terminates in the transit exchange on an FSR which in<br />

turn is connected to either GVI or GVU, or both, according to the direction<br />

<strong>of</strong> traffic and to whether the circuit is one-way or two-way. The same type <strong>of</strong><br />

FSR is used for one-way and two-way outgoing circuits. A two-way circuit<br />

requires very little more relay equipment than an outgoing, and there is<br />

therefore no reason to use separate relay sets for the two types <strong>of</strong> circuit. A<br />

simpler form <strong>of</strong> junction relay set FSIR, on the other hand, is used for oneway<br />

incoming circuits.<br />

The same type <strong>of</strong> junction relay set may be used on two-wire and four-wire<br />

circuits. Matching to existing line signalling systems is effected by the use <strong>of</strong><br />

different types <strong>of</strong> FLR in the repeater station. Translation <strong>of</strong> signals between<br />

the exchange and line sides <strong>of</strong> junction relay sets is standardized. Each twowire<br />

circuit is connected to a combined line and hybrid transformer with<br />

four-wire connection to the exchange side <strong>of</strong> the junction relay set.<br />

FSR and FSIR perform the functions associated with traffic direction,<br />

establishment <strong>of</strong> line connection, repeating <strong>of</strong> signals through the exchange,<br />

supervision <strong>of</strong> the circuit and automatic fault indication. They perform no<br />

123

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