# Protocol Detection for Incoming Calls (S Model Only)

This parameter impacts the treatment of incoming data calls as follows:

- All incoming calls are answered first in voice mode with a prompt requesting DTMF tone or PIN (if configured) entry.
- If a tone has not been entered within 5 seconds (not configurable), the RTU will then attempt a data mode connection.
- The session will then wait the configured maximum time (see keycode 406) for carrier to be established.
- If no carrier signal is detected, the call is terminated.
- If the carrier signal is established the RTU will attempt to identify the protocol used by the calling party for the period of time defined by this parameter.
- During this time period, an appropriate session (Alarmware™, RCS, or MBSLAVE) will begin as soon as the protocol is identified.
- When this time limit expires, one of two things will happen:
  1. If no incoming data was received, the RTU will assume log file download.
  2. If there is incoming data then the RTU assumes a non-RACO SCADA system is calling and a pass-through modem session will begin.

- Subsequent timeouts are controlled by the session timeout limit that will trip if no data is received for that period of time.