Teletype Transmitter, double
<UL>
<LI><b>M707A</b> is a drawing of M707 etch A with a resistor in SERIAL OUT, like M707D.</LI>
<LI><b>M707C</b> is a drawing of M707 etch C.</LI>
<LI><b>M707C+</b> is a drawing of M707 etch C with a resistor in SERIAL OUT, like M707D.</LI>
<LI><b>M707D</b> is a drawing of M707 etch D.</LI>
<LI><b>M707X</b> is a 'modernized' version of M707D.</LI>