1959 - History of Ericsson - History of Ericsson

Fig. 3 x 8181
Block schematic of group selector stage
Sub-stages A, B, C and D
AT auxiliary bay in A stage
Fig. 4
Outgoing group selector bay
120
x 2482
Group Selector Stage
The group selector stage is composed of crossbar switches with ten horizontal
and ten vertical magnets. The crossbar switches are arranged in four
sub-stages A, B, C and D. Sub-stages A and B form incoming group selector
units GVI; C and D form outgoing units GVU. The layout is entirely
symmetrical with the same number of links between each GVI and GVU.
The group selector stage at the Gothenburg transit exchange is made up of
20 GVI and 20 GVU. All four sub-stages are used for establishing a connection.
Since the units are designed for one-way traffic, two-way circuits must
be introduced in one incoming and one outgoing unit. All lines are connected
on a four-wire basis.
The design of the group selector stage allows for variation of the capacity
on the inlet side of GVI and on the outlet side of GVU from a basic capacity
of 100 numbers to 150 or 200 numbers by the addition of supplementary
racks in the A and D sub-stages, known as AT and DT racks.
Register Finder
The register finder RS is made up of crossbar switches arranged in two
sub-stages A and B. The switches are similar to those in the group selector
stage but have an 8-pole instead of 6-pole contact bank.
Every register finder unit is associated with an incoming group selector
unit and no intermediate distribution frame is used between the register
finders and the tandem stage. The number of register finder inlets can be
increased by means of supplementary racks so as to equate the capacity with
that of the associated group selector unit. Every register finder unit has 25
outlets, so that every incoming line has access to 25 registers. The outlets of
the various register finders can be graded together. Through-connection in the
register finder is on 16 wires.
As will be shown, the registers in the Gothenburg exchange must be divided
into two groups. And as the register finders terminate directly on the incoming
group selector units, they too must be divided into two groups as
seen from the trunking scheme in fig. 1.
Register Equipment
The registers are of two types, there being 145 REG-F, which are similar
to the registers in the A-205 transit exchanges, and 60 REG-F-L which are
peculiar to the Gothenburg exchange.
Type REG-F is used for traffic from all exchanges except Gothenburg
local and terminal exchanges. This type of register can receive digits in the
form of dial-type pulses, instantaneous signals from keysets at the Gothenburg
manual positions, and v.f. signals after translation by a code receiver. The