Push-to-talk
Cellular network standards | |||||||||
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| 0G radio telephones (1946) | |||||||||
| 1G (1979) |
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| 2G (1991) |
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| 2G transitional (2.5G, 2.75G, 2.9G) |
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| 3G (1998) IMT-2000 (2001) |
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| 3G transitional (3.5G, 3.75G, 3.9G) |
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| 4G (2009) IMT Advanced (2013) |
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| 5G (2018) IMT-2020 (2021) |
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| Related articles | |||||||||
Push to talk, commonly abbreviated as PTT, is a method of conversing on half-duplex communication lines, including two-way radio, using a button to switch from voice transmission mode to voice reception mode.
Early Use in Mobile Telephony
One of the earliest mobile telephone protocols used PTT. It was the mobile equivalent of operator-assisted land telephone service. The protocol was as follows: The mobile telephone user pressed and held their PTT (Push-To-Talk) button for several seconds to get the mobile operator's attention. When they released PTT, an operator would reply (transmit on their channel) and ask them the number then wanted. The user would key up (PTT) and tell the operator the number they wished. The operator would dial and connect the land line, and the conversation would proceed. When there was no activity for a while or the land line hung up, the operator could reuse the channel. This was used at least into the 1980's in Canada. This was replaced by MTS.
Current Use in Mobile Telephony
The term has come to be more commonly known as referring to a feature that is available on certain more recent mobile phone models. It allows the mobile phone, when in a special mode, to function as a digital two-way radio in push-to-talk operation (in a fashion similar to the "trunking" feature of newer commercial and public-safety two-way radios). Only one person at a time can talk, by pressing a PTT button, and one or several others can listen instantly. The service connects mobile phone users with each other within seconds. Currently, PTT users have to belong to the same mobile operator's (carrier's) network in order to talk to one another. The evolution of the standards will make such interconnection possible in the near future.
When used in GSM networks, the PTT service commonly does not use up the regular airtime minutes that are available for general voice calls.
Nextel Communications introduced mobile push to talk several years ago using iDEN and is currently the leader in this industry.
Verizon introduced the Motorola v60p and v65p mobile phones, modified versions of the v60 that have the push to talk feature, and currently offer the Motorola 300p, Kyocera KX444, and LG VX4700. Sprint PCS is using several models of Sanyo phones equipped with similar technology. Telstra and AIS are using the Nokia 5140 mobile phone and their GPRS networks.
The Motorola, Nokia and Wireless ZT versions of PTT are based on 2.5G packet-switched networks (CDMA by Motorola, GPRS by Nokia and Wireless ZT) and use SIP and RTP protocols. These particular versions of PTT are called "Push to Talk over Cellular", which is abbreviated "PoC".
The Open Mobile Alliance is defining PoC as part of the IP Multimedia Subsystem, and a first version of OMA PoC standard was finalized in first half of 2005.
A pre-standard version of PoC is also defined by the industry consortium made up of Motorola, Nokia, Ericsson, Siemens AG, AT&T Wireless, and Cingular Wireless with the aim of creating a commercial offering enabling inter-operability between vendors.
Several operators, mainly in US and Southern America are using Wireless ZT Open Mobile Alliance and Pre-Standard Push To Talk Server in GSM / GPRS / EDGE networks.
Some operators providing Push To Talk services
- Advanced Info Service (AIS), Thailand
- Bell Mobility (known as 10-4 service) (CDMA)
- Cingular, US (GPRS and CDMA)
- Corr Wireless, US (GPRS)
- Nextel, US
- Personal, Paraguay (known as wolki) (GPRS)
- SouthernLinc, US (iDEN)
- Sprint PCS, US
- Telus Mobility, Canada (known as MIKE) (iDEN)
- Telstra, Australia
- Verizon Wireless, US