Commodore 64 Handbook page 87

standardised -for use on leased telephone-type circuits.
V27 (alternative 2)
4800/2400 bits per second modems standardised -for use in the
general switched telephone network.
V28
Electrical character i sti cs -for unbalanced double-current
interchange circuits.
V29
9600 bits per second modems standardised for use in leased
telephone circuits.
V31
Electrical characteristics for single current interchange
circuits controlled by contact closure.
Data transmission at 48 kilobits per second using 60-108 KHz
group band circuits.
V36
Modems for synchronous transmission using 60— 108 KHz group
band circuits.
85