basically any phone that will work on a regular phone line will work on a T/R module.
Single-Line
Telephone
Industry-standard touch-tone or rotary dial telephone that
handles one call at a time. It is connected to the system via
an extension jack on an 012 (T/R), 016 (T/R), or 008 OPT
module; or, in Release 7.0 and later systems, via a port on
a 412 LS-ID-ETR or 016 ETR module programmed for tip/
ring operation.
(All modes) Current 012 (T/R), 008 OPT, and 016 (T/R)
modules have built-in ring generators and are compatible
with earlier releases. The 012 (T/R) module [517J13 (28)]
has a ring equivalency number (REN) of 2.2 and rings only
four ports at a time, although eight jacks can be used for
applications. The 016 T/R module (517C34) has a REN of ≥
4, can ring 16 ports at a time, and has no restriction on the
number of jacks that can be used for applications. The 412
LS-ID-ETR and 016 ETR modules (Release 7.0 and later
systems) have a REN of 3 and can ring all tip/ring ports at the
same time.
.....
On older versions of the 012 (T/R) module (apparatus codes 517C13–
517J13), only four tip/ring devices connected to the module can ring
simultaneously, regardless of how many jacks are open. Using more
than four devices can cause the devices to operate incorrectly.
When Linux is Free and Open, who needs Windows or Gates?