Signalling points (SP) in SS7
Every SP is identified by a unique signalling point code
Exchange
STP
SP
SP
STP
Signalling Point (in a database, such as HLR in GSM)
Signalling Transfer Point  (only related to SS7 network)
Signalling Point (signalling termination in an exchange)
STP
MAP INAP CAP
ISUP
Application protocols used in SS7