Cisco Catalyst 1900: Can You Do Trunking With This Switch?

Well, the short answer is Yes AND No.  I went onsite with another engineer and found that the request that was being made was to add a IP Phone (a Yealink) to the voice vlan of the Cisco infrastructure.  In these trailers, they had two Cisco 1900s and one Cisco 2600.  Pretty old stuff.  So, do these older switches support trunking?  See the topology, then lets discuss more.

Yes, the 2600 does support trunking.  It has one command that is slightly different, of which I can not recall at this time.
Yes and No on the 1900s.  Yes, the 1900 can do trunking IF you have the Enterprise version of IOS.  If you have the Standard version, then the answer is No.  Here is what the documentation says:
The Catalyst 1900 runs two versions of images, namely the Standard and Enterprise editions. Trunking is only supported on the Enterprise images, and it only supports ISL encapsulation and does not support 802.1q. This limits the capability of the Catalyst 1900 to form a trunk with other Catalyst switches that can support ISL trunking. Furthermore, trunking can only be configured on the two x 100 Mbps uplink ports on the Catalyst 1900. These are the last two ports on the switch normally marked Ax and Bx. You can configure up to 1005 VLANs on the Catalyst 1900 Enterprise image. The Command Line Interface (CLI) (similar to the Cisco IOS® CLI) is only available on the Enterprise image of the Catalyst 1900.

Oh, and here is a small look at what the console looks like, just in case you are curious:

        Catalyst 1900 - Main Menu

     [C] Console Settings
     [S] System
     [N] Network Management
     [P] Port Configuration
     [A] Port Addressing
     [D] Port Statistics Detail
     [M] Monitoring
     [B] Bridge Group
     [R] Multicast Registration
     [F] Firmware
     [I] RS-232 Interface
     [U] Usage Summaries
     [H] Help

     [X] Exit Management Console


Enter Selection:  F