ISDN Data and Telephony Protocol Engine (inc. X.25)
CMX228
1.5.5 POTS Operation
1.5.5.1 Keypad Operation
The CMX228 supports ISDN keypad messages for control of Network Supplementary services either
before or during call establishment. When dialling a number (ie off-hook and dial tone audible on
POTS port), or if a call has been disconnected by the network but the POTS port has not yet gone on-
hook, any keypad string entered will be sent to the network as ‘Keypad Information Elements’ within
INFORMATION messages. Keypad strings are defined as the following sequences of digits, with the
exception of the configuration strings defined in the previous section:
S...#
S#...#
#...#
When a call is connected, pressing the recall key results in all subsequent key presses being sent to
the network as ‘Keypad Information Elements’ within INFORMATION messages, until the handset is
replaced. The tones generated by the key presses are also passed down the B-channel, so the
remote user will be able to hear them.
1.5.5.2 Incoming POTS Calls
An incoming POTS call is identified by the Bearer Capability Information Element of the SETUP
message being set to ‘Speech' or ‘3.1 kHz Audio’. The call will be routed to the POTS port if it
satisfies the following three conditions:
·
·
The port is on-hook.
The MSN saved for the port matches the Called Number in the incoming SETUP message, or
no MSN is specified for the port, or there is no Called Number in the SETUP message. See
section 1.5.3.5 for details of POTS port MSN selection.
·
The ISDN B-channel on which the call is placed (as indicated in the SETUP message) is
compatible with the channel mapping configuration for the port. See section 1.5.3.6 for details
of POTS port channel mapping selection.
When the call is routed to the port, the ringing signal for that port will be applied by means of the
RINGP1 and RINGN1 pins.
The call is answered when the port with ringing signal goes off-hook. The ringing signal is then
stopped and the ISDN call is connected to that port.
1.5.5.3 Outgoing POTS Calls
Outgoing calls are initiated when the POTS port goes off-hook. An ISDN SETUP message is sent to
the network with the Bearer Capability Information Element set to 'Speech'. The dial tone presented by
the network on that ISDN B-channel which was selected by channel mapping (see section 1.5.3.6), will
be routed to the POTS port.
When DTMF tones are received from the POTS port, they are sent to the network either as Called
Party Number or Keypad Information Elements. Keypad Information Elements are discussed in
section 1.5.5.1.
Receipt of a valid DTMF tone will prompt its conversion to IA5 coded digits, as shown in the following
table (IA5 hex digits are in brackets). If the first valid digit to be received is a ‘S’ then the configuration
mode is entered and subsequent digits will be monitored and saved as indicated in section 1.5.4.1. If
the first tone received is not a ‘S’ or ‘#’ (see section 1.5.5.1) that digit and all subsequent digits will be
passed to the network in an INFORMATION message as a Called Party Number Information Element.
ã 1999 Consumer Microcircuits Limited
ã 1999 Chiron Technology Limited
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CMLMICRO [ CML MICROCIRCUITS ]
