This sub-class deals with methods, circuits, or apparatus for establishing selectively a connection between a desired number of stations (normally two), or between a main station and a desired number of substations (normally one) for the purpose of transferring information via this connection after it has been established. The sub-class also deals with selective calling arrangements over connections already established. In either case, the connection may be by means of electric conductors or electromagnetic waves.
In this sub-class:
"Subscriber" is a general term for terminal equipment, e.g. telephone for public use.
"Substation" means a subscriber or monitoring equipment which may connect a single subscriber to a line without choice as to subscriber.
A "satellite" is a kind of exchange the operation of which depends upon control signals received from a supervisory exchange.
"Switching centres" include exchanges and satellites.
in which m-out-of-n signalling frequencies are transmitted [3]
H04Q 1/457
· · · · · ·
with conversion of multifrequency signals into digital signals [3]
H04Q 1/46
· · · · ·
comprising means for distinguishing between a signalling current of predetermined frequency and a complex current containing that frequency, e.g. speech current
Signalling by currents in one or other or both line wires or additional wires
H04Q 5/06
· ·
Signalling by amplitude or polarity of dc
H04Q 5/08
· ·
Signalling by continuous ac
H04Q 5/10
· · ·
using single frequencies for different subscribers
H04Q 5/12
· · ·
using combinations of frequencies
H04Q 5/14
· ·
Signalling by pulses
H04Q 5/16
· · ·
by predetermined number of pulses
H04Q 5/18
·
with indirect connection, i.e. through subordinate switching centre
H04Q 5/20
· ·
the subordinate centre permitting interconnection of subscribers connected thereto
H04Q 5/22
· ·
the subordinate centre not permitting interconnection of subscribers connected thereto
H04Q 5/24
·
for two-party-line systems
H04Q 7/00
Selecting arrangements to which subscribers are connected via radio links or inductive links
H04Q 7/02
·
for subscribers using radio or inductive link only
H04Q 7/04
·
with possibility of connection to and from line exchanges
H04Q 9/00
Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom