Instruct: Classify a given review into positive or negative sentiment.
Query: useless

PC Telephony is the "manual" of Parity Software's VOS program and is targeted at novice PC telephony programmers. The book describe briefly several Dialogic boards that and the way VOS override C Programming. The book is interesting for those wishing to test or adopt Parity's VOS for programming their Dialogic Boards... BUT recently Parity released its new version of VOS. Spend your money on another book !