Yep good point...
Being a newbie, after posting this message - I did additional searches of other postings and news groups and discovered using 'minicom' was an alternative way of testing my configuration.
And... it works! DOH!
As my PCMCIA GSM modem also supports voice, my final challenge is to work out how accomplish voice XOR data communications. With data, I'm using the AT command set augmented by the ETSI command set of 07.05 and 07.07. With voice ... well I'm looking into it and again, it's probably something real simple.