tone. Sometimes systems using Selcall are referred to as CCIR or ZVEI, specific tone encoding schemes used in Selcall systems. On the continent, people use the ZVEI scheme while in Great-Britain the CCIR is very common. In the same way that a single CTCSS tone would be used on an entire group of radios, a single five-tone sequence is used in a group of radios. All radios also have their own private callnumber stored, to be reached for an individual conversation instead of a group call. In either way the radio speaker turns on as soon as the fifth tone of a valid sequence is decoded. In case of a group call, a short announcement tone is generated on the radios speaker. In case of a private call, the receipt tone is transmitted back to the sender and then the receive path is open. The speaker stays on until the carrier squelch detects that the carrier is no longer being received. At that point, the speaker mutes and the decoder resets. The receiver speaker turns off and remains muted until another valid five-tone sequence is decoded. A similar tone format is used for one-way tone-and-voice radio paging in the US. It is informally known as Reach format. DCS DCS or Digital-Coded Squelch superimposes a continuous stream of FSK digital data, at 134.5 baud, on the transmitted signal. In the same way that a single CTCSS tone would be used on an entire group of radios, the same DCS code is used in a group of radios. DCS is also referred to as DPL tone (for Digital Private Line, a trademark of Motorola), and likewise, GE's implementation of DCS is referred to a Digital Channel Guard (or DCG). Some equipment uses a 136 Hz square wave turn off code. The turn-off signal is sent for one- to three-tenths of a second (100–300 ms) at the end of a transmission to mute the audio so that a squelch crash is not heard. Radios with DCS options are generally compatible provided the radio's encoder-decoder will use the same code as radios in the existing system. Codes are usually described as three octal digits, (for example, 054). Some DCS codes are inverted data of others: one code with the marks and spaces inverted may form a different valid DCS code (413 is equivalent to 054 inverted). Because of the use of the 136 Hz