Hi Joseph,
This would be configured using the "button" (s=silent separator) command;
From;
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucme/command/reference/cme_cr/cme_b1ht.html#wp1050318
Cheers!
Rob
button
To associate ephone-dns with individual buttons on a Cisco Unified IP phone and to specify line type or ring behavior, use the button command in ephone configuration mode. To remove an ephone-dn association from a button, use the no form of this command.
button button-number {separator} dn-tag [,dn-tag...] [button-number{x}overlay-button-number] [button-number...]
no button button-number {separator} dn-tag [,dn-tag...] [button-number{x}overlay-button-number] [button-number...]
Syntax Description
button-number | Number of a line button on a Cisco Unified IP phone that is to be associated with an extension (ephone-dn). The maximum number of button-ephone-dn pairs is determined by the phone type. Note  The Cisco Unified IP Phone 7910G has only one physical line button, but you can assign it two button-ephone-dn pairs. |
separator | Single character that denotes the characteristics to be associated with this phone button. Valid entries are as follows: •: (colon)—Normal ring. For incoming calls on this extension, the phone produces audible ringing, a flashing icon in the phone display, and a flashing red light on the handset. On the Cisco IP Phone 7914 Expansion Module, a flashing yellow light also accompanies incoming calls. •b—Beep but no ring. Audible ring is suppressed for incoming calls, but call-waiting beeps are allowed. Visible cues are the same as those described for a normal ring. •c—Call waiting. Provides call waiting for secondary calls to an overlaid ephone-dn. See also the o keyword. •f—Feature ring. Differentiates incoming calls on a special line from incoming calls on other lines on the phone. The feature-ring cadence is a triple pulse, as opposed to a single pulse for normal internal calls and a double pulse for normal external calls. |
| | •m—Monitor mode for a shared line. Visible line status indicates whether the line is in-use or not. Monitored lines cannot be used on this phone for incoming or outgoing calls. •o—Overlay line. Multiple ephone-dns share a single button, up to a maximum of 25 on a button. See also the c keyword. •s—Silent ring. Audible ring and call-waiting beep are suppressed for incoming calls. The only visible cue is a flashing ((< icon in the phone display. Note In Cisco IOS Release 12.4(4)XC and later releases, the silent ringing behavior is overridden during active night-service periods. Silent ringing does not apply during designated night-service periods when the s keyword is used. •w—Watch mode for all lines on the phone for which this directory number is the primary line. Visible line status indicates whether watched phone is idle or not. |
dn-tag | Ephone-dn tag that was previously defined using the ephone-dn command. When used with the c and o keywords, the dn-tag argument can contain up to 25 individual dn-tags, separated by commas. |
x | Separator that creates an overlay rollover button. When the overlay button specified in this command is occupied by an active call, a second call to one of its ephone-dns will appear on this button. This button is also known as an overlay expansion button. |
overlay-button-number | Number of the overlay button that should overflow to this button. |
