Have another Trimline that does't dial out.

[princessphone]

Hi there,
Just bought another red Trimline that will not dial out (This was disclosed by seller). Price was right, very nice condition, round button TT, all dates match '73. Appears not to have been worked on nor refurbished.
Rings, takes calls, has dial tone but when dialing no touch tone sounds (DTMF) are heard. When any button is depressed there is silence, and when released the dial tone returns.
Reversing polarity did not help. Other handsets work with the base unit.
Can anyone perhaps shed some light on the problem?
Thanks, John DeJonge