Can I use Lyric as a keypad on 15P, 20P, 21iP, 128bpt?

No, the Lyric Controller is a stand-alone, all-in-one wireless alarm system with a built in touchscreen interface, as well as a built-in wireless receiver, Z-Wave module, WIFI communicator, and even a built-in camera. There is no keypad bus on the Lyric Controller, so it can neither have wired remote keypads, nor can it behave as one for another system.

The Vista series panels, from Honeywell, are more traditional systems, with hardwired inputs, and outputs. There is a keypad bus on each, where keypads, receivers, and other input/output devices are connected to the panel. In order to use a touchscreen interface on these panels, you need a Tuxedo Touch, or similar keypad, which will be wired to, and addressed on, the keypad bus. Vista panels have a more modular design. They come with a certain number of hardwired zone inputs, a hardwired bell output, and you can then add additional inputs or outputs, either wired, or wireless, as the need arises. If you never intend to have wireless zones, then there’s no need to install a receiver, for example. These systems seem less expensive at first glance, but when you begin to add features, and with features, various modules, the value of the Lyric Controller soon becomes apparent.