Analog Voice Ports

Analog - one call per port.

FXS - Foreign Exchange Station - analog phone/fax/modem

FXS-DID - Direct Inward Dial - only supports inbound calls

FXO - Foreign Exchange Office - analog phone line from the provider

E+M- Ear and Mouth - bridge to a PBX system

CAMA - Centralised Automated Message Accounting - emergency dialling - ANI (Caller ID)

Signalling

Non-voice data

• Supervisory (on/off hook)
• Addressing (Digits, DTMF)
• Informational (Busy, Ring)

FXS/FXO

• loop-start - connecting wire by lifting the phone - common on PSTN
• ground-start - connection needs to be grounded to start - common on PBX

E+M

• Operation (2/4 wire)
• Type (1-3,5)
• Signalling
  • Immediate
  • Wink
  • Delay-start

Ports are active by default; port configuration is not normally needed for FXS/FXO

E+M needs to be configured to match the PBX end.

Show all voice ports: show voice port summary

voice-port 1/0/0
  signal loopStart
  cptone GB
  ring cadence pattern01

Call progress tones can be changed to match the region.

Port can be set to automatically dial a number

voice-port 1/0/0
  connection plar 1000

Reducing Echo

Usually caused by a 2-to-4 wire conversion

PSTN calls have low delay (<25ms), Echo is not noticeable.

• IP network can add delay before it his the PSTN
• Echo cancellation (ITU-T G.168) goes on the voice gateway
• Enabled by default
• Can increase the coverage

voice port 1/0/0
  echo-cancel coverage 64
  echo-cancel erl worst-case 3

Analog Timers

• timeouts initial
• timeouts interdigit
• timeouts ringing
• timing digit/interdigit (DTMF)
• timing hookflash-in/hookflash-out

Verification commands

show voice call summary

show call active voice

show call history voice