INT 61 - Banyan VINES - CHECK SERVICE
        AH = 01h
        AL = service ID (see below)
Return: AX = status
            0000h installed
            0001h not installed
            0002h invalid ID

Values for service ID:
 01h    communications
 02h    primary 3270 emulation
 03h    async terminal emulation
 04h    file deflection
 07h    StreetTalk
 08h    environment
 0Ah    secondary 3270 emulation
 0Bh    semaphore service
 0Ch    3270 emulation active status
 0Dh    3270 keyboard interrupt simulator

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