Try these:
<http://bitsavers.trailing-edge.com/pdf/ti/terminal/960129-9701_Rev_E_Silent_700_Model_732_733_ASR_KSR_Maintenance_Manual_Nov_1977.pdf>
<http://bitsavers.trailing-edge.com/pdf/ti/terminal/TI-323H-2M_Bulletin_323H_Silent_700_Price_List_Dec_1973.pdf>
IIRC, based on this price list, the difference between the different
models listed there has more to do with the additional options than the
guts of the terminal.
For instance the 733 is the same base model terminal unit with the
dual cassette drives added on top for "automatic send/receive". The
725 is the terminal guts mounted in a suitcase type enclosure with an
acoustic coupler. The 720 is the terminal guts mounted in an
enclosure similar to the 733 but with an RS-232 interface.
Really, I don't think the different "models" are radically different
in terms of the terminal guts, just what extra goodies are arranged
around it and how it is packaged in an enclosure.
I haven't put this idea to the test yet, but you should look at the
733 maintenance manual.
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