Previously I have written a post about hotline configuration but that configuration example uses none partition which Cisco does not recommend.
So here I shall re-do the post in creating a hotline configuration example by not using none partition for my telephones.
From CUCM, Call Routing > Class of Control > Partition
Creating a partition by giving it a name. Phones that reside in the same partition can call to each other.
Create a calling search space (CSS)
From CUCM, Call Routing > Class of Control > Calling Search Space
Include the HOTLINE-PART and PART-RED into the CSS. Since both telephones reside in the same PART-RED partition PART-RED must be included in order for the hotline phone to call.
Create a translation pattern
From CUCM, Call Routing > Translation Pattern
The translation pattern should include the HOTLINE-PART partition and HOTLINE-CSS calling search space.
The translation pattern should also have the directory number to call to when the hotline phone off-hook button is pressed or when handset is removed.
Apply onto the hotline phone
From CUCM, Device > Phone
Under the device information, the HOTLINE-CSS should be included into the calling search space. The CIPC and 7940 are residing in the same partition, the HOTLINE-CSS should also contain the partition that both phones reside otherwise the hotline phone will not be able to dial the directory number.
Partition and calling search space of CIPC and 7940
7940 IP phone
There is no need to include any calling search space under device information, the CSS and the partition are applied to the directory number under association information.
The CIPC directory number resides in the same partition as the 7940 directory number and they have the same calling search space.