Interconnection arrangements between switching centres (transmission arrangements in general H 04 B)
7
/
02
•
for compensating differences of ground potential
7
/
04
•
for compensating differences of line impedance
7
/
06
•
using auxiliary connections for control or supervision
7
/
08
•
for phantom working
7
/
10
•
for two-way working, i.e. calls may be set-up in either direction over the same connection
7
/
12
•
for working between exchanges having different types of switching equipment, e.g. power-driven and step by step, decimal and non-decimal
7
/
14
•
in systems involving main and subordinate switching centres (current supply source at subordinate switching centre charged from main exchange H 04 M 19/06
)
7
/
16
•
in systems employing carrier frequencies
9
/
00
Interconnection arrangements not involving centralised switching
9
/
02
•
involving a common line for all parties
9
/
04
•
involving a separate line for each pair of parties
9
/
06
•
involving combinations of interconnecting lines
9
/
08
•
Two-way loud-speaking telephone systems with means for suppressing echoes or otherwise conditioning for one or other direction of traffic (for line transmission in general H 04 B 3/20)
9
/
10
•
•
with switching of direction of transmission by voice frequency
11
/
00
Telephonic communication systems adapted for combination with other electrical systems
11
/
02
•
with bell or annunciator systems (such systems in general G 08)
11
/
04
•
with fire, police, burglar, or other alarm systems (such systems in general G 08)
11
/
06
•
Simultaneous speech and telegraphic or other data transmission over the same conductors (transmission of digital information in general H 04 L)
11
/
08
•
adapted for optional reception of entertainment or informative matter (systems in which the information is continuously available on a carrier over the whole network H 04 H 1/08)
11
/
10
•
with dictation recording and playback systems (such systems in general G 11 B)
