The operation of most of repeaters is supervised by a microprocessor-based repeater controller. The controller provides a number of functions such as activating the repeater transmitter when a valid signal is present on the repeater receiver, periodically identifying the repeater station by CW or speech, and limiting the duration of transmissions via a time-out timer. Users of the repeater need to be cognizant of a few of these functions and how their transmissions have an effect on, or are affected by, the repeater controller.
When a station first keys up to make a transmission through a repeater, there is an inherent delay between the time they activate the push-to-talk (PTT) switch on their radio, and when other stations hear the transmitting station's audio. When the PTT is activated, there is a delay associated with the user's radio switching from receive mode to transmit mode. It then takes time for the repeater receiver's squelch to open, and for the PL tone to be decoded, after which time the repeater transmitter is keyed up (if not already active), and the audio gate through the repeater is opened to pass audio from the receiver to the transmitter. At the receiving station, there is a delay associated with the squelch opening and PL decode acquisition (if used). In total, from the time the transmitting station keys the mic to the time when audio can actually be heard by the receiving station, the delay is on the order of one second. As such, when making a transmission on a repeater, key the mic and wait at least a second for before speaking, otherwise the start of your transmission may never be heard. On linked systems, waiting even longer before speaking is often necessary as the delays incurred across the link paths are cumulative.
Repeaters have time-out timers that limit the maximum duration that a user's transmission will be repeated. The time limit is programmed by the repeater owner or control operator based on their preferences, and typically ranges between one minute and three minutes. Should a station make a transmission that exceeds the time-out timer limit, the repeater is put into a disabled state that is often preceded by a controller-generated message indicating that the time-out timer has been exceeded. After the user who has "timed out" the repeater stops transmitting, the controller will re-enable the repeater, and in most cases, announce again that the time out timer has been exceeded so that the offending station is aware of what transpired while they were transmitting. Violating the time-out timer is poor practice. Most modern radios can be programmed to have a time-out timer on their own to prevent timing out the repeater - take advantage of it, not only to avoid timing out repeaters, but also to prevent transmitting unintentionally for an extended period of time such as if the microphone PTT switch is activated accidentally by "sitting on the mic". While on the subject, a hand-held microphone should be kept on its mic hanger or hang-up clip when not in use to prevent inadvertent activation of the PTT switch.
Most repeaters have a courtesy tone which sounds between user's transmissions. During the normal course of communications on a repeater, each time a user unkeys (stops transmitting), several sequential events occur First, there is a period of time, typically on the order of one second, during which the repeater transmits silence. This is referred to as the courtesy tone delay. After the courtesy tone delay, the courtesy tone is sent out the repeater transmitter. The courtesy tone serves several purposes. First, it notifies all listening stations that the previous station has finished making a transmission, and that the next station to transmit should proceed. Second, it provides an opportunity for a station not currently participating in the discussion to break in, either to join the conversation or to make a call. Finally, once the courtesy tone sounds, the time-out timer is reset. It is imperative that when a user unkeys that the next station to transmit waits for the courtesy tone before making the next transmission, otherwise others will not have an opportunity to break in, and the time-out timer will not be reset. Not waiting for the courtesy tone to sound before transmitting is referred to as "quick keying"; it is poor operating practice, and typically a violation of the rules of the repeater.
After the courtesy tone sounds, unless another station transmits, there is again a period of silence, typically on the order of several seconds, before the repeater transmitter unkeys or "drops". This is referred to as the "hang time". During the hang time is when the next station to transmit should begin his or her transmission. The purpose of the hang time is to prevent the repeater transmitter from unkeying and rekeying repeatedly during the course of a conversation. Each time the repeater transmitter keys and unkeys there is additional wear and tear on electromechanical devices such as relays and cooling fans, additional stress to components due to thermal cycling and inrush current, delays that result in the start of the next transmission potentially being "cut off" due to the time it takes for the squelch to open, PL decoder to recognize the signal, and in the case of linked repeater systems, for all of the repeater transmitters to also come back up, etc.. Purposefully waiting until the repeater transmitter drops out before making a transmission defeats the purpose of the hang time and is extremely poor practice.
