Missing + character problem

Alf Fisher

Hello Group,
This is my first posting on here so I hope I get it right.
For some years I've been using the wonderful MMTTY program to send text messages to the serial port on a laptop that is connected via an opto isolator to a Creed 7B teleprinter.
It all works fine except that plus signs are not printed.  There may be other characters as well but I haven't found those.
Watching the sequence of characters being sent on the laptop screen and when it encounters the + sign in the text message, it does nothing.  It is a non-printing character.
The ASCII value for a plus sign is 2B Hex is correct but it isn't in the character set for MMTTY.
Does anyone know what character set is used in MMTTY? 
On the machine, the plus sign is a shifted Z and the machine's character set is that of CCITT No. 2  International 5 unit teleprinter code but this obviously isn't what is programmed into MMTTY.
I think MMTTY needs the option to choose different character sets and it looks like I need CCITT No.2 .

Can anyone help please?

Best regards,

Alf, G3WSD