Avaya INDeX 11.0 Manual Do Utilizador

Page 4 - Introduction 

MF & Time Break Recall operation 

The 20AT uses MF signalling and TB recall signalling only. Contact your telephone 

line provider if unsure of the type of signalling you should be using. 
During a call, phones can use a recall signal to indicate to the exchange that they 

are about to send more digits. 
 

To ring properly when a call arrives all phones draw a small current from the 

telephone line. All telephone devices have a REN value, a measure of how many 
'current units' they need to ring properly.  
Most telephone lines can provide ringing current for a total REN of 4. If the total REN 
of all the devices on the line exceeds that value, then some of the devices may not 

ring when calls arrive. 
If it is necessary to connect more devices to a line than it can support, equipment 

exists that can increase the total REN provided by the line. Contact your line 
provider for details. 
•  The 20AT has a REN of 1. It can share the same telephone line as other 

telephone devices so long as the total REN does not exceed that of the line 
(usually 4). INDeX standard telephone sockets provide a REN of 2. 

 

The apparatus is approved for connection to the PSTN or suitable PBX supporting 

DTMF signalling. 
The 20AT has been approved for use of the following facilities: 

•  DTMF signalling. 
•  Mute. 
•  Dual level receive volume control. 

Any other usage will invalidate the approval of the apparatus if as a result it then 

ceases to comply with the standards against which the approval was granted. 
This apparatus is capable of 999/112 calls to the emergency services. 

Page 4 - Introduction 

INDeX 11.0 20AT Telephone User's Guide 

MF & Time Break Recall operation 

38DHB0002UKHB Issue 1 (10/05/2004)