47 CFR § 80.71 - Operating controls for stations on land.
(a) Each station using telegraphy or telephony must be capable of changeover from transmission to reception and vice versa within two seconds excluding a change in operating radio channel.
(b) During it hours of service, each station must be capable of:
(1) Commencing operation within one minute after the need to do so occurs;
(2) Discontinuing all emission within five seconds after emission is no longer desired. The emission of an unattended station in an automated multistation system at which restoration to standby is automatic on conclusion of a call must be discontinued within three seconds of the disconnect signal or, if a disconnect signal is not received, within twenty seconds after reception of the final carrier transmission from a ship station.
(c) Each station using a multichannel installation for telegraphy must be capable of changing from one telegraphy channel to any other telegraphy channel within the same sub-band below 525 kHz within five seconds. This requirement need not be met by equipment intended for use only in emergencies and not used for normal communication.
(d) Every coast station using a multi-channel installation for radiotelephony must be capable of changing from one telephony channel to another telephony channel within:
(1) Five seconds within the frequency band 1605-3500 kHz; or
(2) Three seconds within the band 156-162 MHz. This requirement also applies to marine utility stations.