Cisco Systems 2600 appendix VC-821, Command, Purpose, dsp-pre-alloc

Caller ID on Cisco 2600 and 3600 Series Routers and Cisco MC3810 Multiservice Concentrators

Caller ID Configuration Task List

	Command	Purpose
Step 4
	Router(config-voiceport)# caller-id alerting	(FXO ports, only when caller-ID alerting
	dsp-pre-alloc	line-reversal is required) Configure this command
		on the FXO port when the incoming subscriber
		telephone line uses line polarity reversal to signal
		the start of caller-ID information transmission.
		The Cisco FXO interface cannot detect
		line-reversal alerting in the on-hook state. For this
		reason, DSPs must be pre-allocated to serve the
		Type 1 caller ID information when it arrives.
		Preallocating the DSPs enables the DSP to
		continuously monitor for the arrival of caller-ID
		information.
Step 5
	Router(config-voiceport)#caller-id alerting pre-ring	(FXS ports only) Configure this setting only when
		the attached telephone device requires the pre-ring
		(immediate ring) method to signal the start of a
		caller ID information. The command activates a
		250-ms pre-ring.

Cisco IOS Voice, Video, and Fax Configuration Guide

VC-821