a notch filter at the base station blocks the steady 2,175 Hz tone from going out on the air. Proper levels for tone remote systems are 0dbm for the high level tone, -10dbm for the function tone and -30dbm for the low level guard tone (Motorola's older manuals often confused technicians with some levels listed as high as +14dbm. Analog telephone circuits used by tone remote systems normally only allow 0dbm as a maximum) All levels are based on 600 ohm impedance termination at the radio itself and needed gain after a long circuit to bring the levels back up to the levels noted above. Level discipline varies from one system to another. In order to get the transmitter to key reliably, sometimes the continuous tone that holds the transmitter on may have to be set so it is heard in the transmit audio. Sometimes equalization problems with a telephone circuit make it necessary to run higher levels than a circuit with a flat response from 300 to 3000 Hz would require. Normally a phone circuit ordered as a PLPA or conditioned type results in a 300 to 3400 Hz response which easily handles all tones used in a tone remote radio system. Normal LMR practices of running the levels hotter than normal is something to be avoided to prevent an audio problem later if equipment is changed out. Audio level compression Remote control consoles use audio level compression in transmit and receive audio paths. In documentation for most any console, receive audio is described as having a 30 decibel (db) knee of compression: for a 30 db variation in input audio level, the speaker volume changes by 3 db. This is desirable because persons calling on the radio who are whispering or yelling would ideally be intelligible and be presented to the console user at roughly the same volume. It helps reduce the need to constantly adjust the volume control to accommodate different voices. It also helps the console user talk on the telephone without loud sounds coming from the remote control speaker. A professional dispatcher will often set the console volume at a setting similar to the telephone's perceived volume. This allows the dispatcher to shift her attention between the radio and the phone without continually adjusting volume controls during a conversation. Transmit audio is compressed so that field units can hear the base station user over background