This is a Work In Progress
The Tait TB7100 is an FM repeater. It's a relatively simple device made up of two TM8100 series radio boards, a “User Interface” board that allows the operator to change channel etc, and a “System Interface” board that does some some signal conditioning, basic logic, and fan control.
As you'd expect from Tait, a plethora of IO is broken out on a DB25 connector on the rear of the repeater.
A batch of Multitone pager transmitters have recently appeared on eBay. These are a TB7100 chassis with a single 50w VHF radio fitted on the transmit side, and an additional “paging interface board” to re-map some of the internal connections and condition the incoming AFSK paging signal before its transmitted.
As-is they're probably not much use to amateurs as paging is commonly on UHF and other applications will require access to the Rx audio, but it's relatively easy to either convert them back into a duplex repeater, or re-route the connections internally so we can access both the Tx and Rx audio on the single radio.
In my opinion this is worth the effort, as the chassis provides a nice 1U rack mount platform with power distribution and suitable cooling for high duty cycle operation, and room for some combination of a duplexer, AC power supply, NinoTNC, MMDVM, or Raspberry Pi.
To convert the pager transmitter into a duplex repeater, you will need to transplant in an Rx radio, 3x ribbon cables, a DC power lead, and appropriate coax / connectors / duplexer (optional)
If you're planning to use the TB7100 for simplex use (Packet node, analogue gateway, etc) you'll probably want to remove the Multitone Pager Interface to free up some room in the enclosure. Unfortunately it's not quite as simple as just removing it, as without it the UI interface will malfunction. This is because in normal operation it takes 13.8v and 3.3v from the Rx radio, which is absent. As a workaround, the pager interface takes 13.8v from the aux connector on the Tx radio, drops it down to 3.3v, and supplies both these voltages to the Rx connector on the UI board. It's also not possible to monitor the receive audio on the Tx radio, as this is hardwired to the Rx side.
To fix these issues, we can instead split the signals and voltages coming from the connector on the Tx radio control head connector, and shuffle them around so everything's in the correct place. This will also free up the aux connector on the Tx radio for interfacing with your TNC or other controller.
Note: This solution is slightly half baked. The connections to the system board will be removed, meaning it will only be providing DC distribution and fan control - There will be no I/O exposed on the system connector. If you need more space you could remove the system board entirely, or if you need the I/O you could perform some additional re-mapping internally, but as availability of these particular pager transmitters has dried up, we'll go with a quick solution for now.