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Direct Mode DECT:
For additional information on Direct Mode (Walkie Talkie Mode) please click here
Direct Mode seems to be one of the best-kept secrets of DECT telephony. With minor changes to the software, DECT phones can be enabled to talk to each other in direct 'walkie-talkie' mode, enabling you to take your DECT phones with you and keep in touch with your partner or kids as you split up and wander around the shopping centre. Obviously this will only work as long as you stay within range, (typically 100m) - however, DECT phones can be enabled, as indeed some already are, to alert the user when he goes out-of-range.
DECTweb is very grateful to Guenter Kleindl, who leads ETSI's DECT standardisation team, for providing the information included in this feature. Who knows, maybe it will prompt some manufacturers to add such features to their phones, as they seek a competitive edge in today's price-driven domestic market, to the benefit of the end users.
If there is a demand for more information or discussion of Direct Mode, DECTweb may endeavour to see if we can persuade Gunther Kleindl to join us for an on-line chat session - if you would welcome this please e-mail DECTweb, so we can ascertain the potential interest.
Baseline Information Sources
To aid the understanding of the text below, here a quick guide to DECT ETSI-speak:
Requirements for PPs with Direct PP to PP Communication Mode
1. Description of Operation in Direct PP to PP Communication
The access rights class E and related PARK E are reserved for direct communication only, see EN 300 175-6  second edition, subclauses 5.5, 6.1.5 and 6.3.2. The Access Rights Identity (ARI) class E requires a key pad entry of only 5 digits to provide all identity and subscription data required to form a group of PPs for direct communication. The use of class E identities is normally of temporary nature and does not contain an ETSI distributed code.
When there is no communication all PPs are active unlocked, no (dummy) bearer transmission exists, and all PPs are regularly, e.g. every 10 seconds, scanning all access channels with carrier numbers c < 10, for a (dummy) bearer transmission with proper Radio Fixed Part Identity (RFPI). When a PP wants to initiate a connection, it acts like an RFP, selects a channel within carriers c < 10 and starts transmitting a simplex (dummy) bearer with the relevant page message and Q T information. Only the paged PP is allowed to enter idle locked mode, and shall respond with a normal bearer setup. If ARI class E is used, the initiating PP is not required to perform receiver scanning, and the paged PP shall make the bearer setup attempt on the channel pair where it received the paging and intracell handover is not possible. The initiating PP shall seize transmitting and revert to PP active unlocked state, if a duplex bearer has not been established within 20 seconds. The initiating PP, when acting as an RFP, is allowed to apply PP timer stability requirements and PP channel selection rules for simplex bearers. A PP entering RFP mode is also allowed to derive over the air slot synchronization from a "non ARI E" DECT system, e.g. a large office system.
2. Testing Requirements
2.1 Setting the PP In Direct Communications Mode
The applicant shall inform the test laboratory about the applied identities and the value of T, see below.
When not processing a call, the EUT shall be in active unlocked PP state. When initiating a call the number of the wanted subscriber shall be entered via the key pad, and the EUT shall at off-hook enter the RFP active idle state continuously sending the page message for the wanted subscriber. See EN 300 175-3 , subclause 4.3.
When the EUT has Initiated a Handset-to-Handset Call
When in RFP Active Idle State:
2.3 When the EUT has Not Initiated a Call