It's been a while, but I think you can only do this via the RDR gate opener in LD 15 and using the RCO feature on the Door Phone.
You should have 3 settings each for internal and external calls.
These are the ring cycles set as values 0, 1 and 2 and most sites will stick with the initial "0" one. This means that the RCO value will be set to "0" on the Door Phone.
It should just be a case of changing the ringing values for the other options assuming that no one else is using them of if one of them already has the number of rings that you require, then you can just change the RCO value against the set.
In LD 15 the settings will be something like this below.
>LD 21
REQ: PRT
TYPE: CDB
RDR_DATA
OPT CFO CFRA DSTD PVCA CWRD MCX
FNAD FDN
FNAT FDN
FNAL FDN
CFTA NO
CCFWDN
CFN0 4 ##### The CFNx prompts are the 3 internal ring cycles #####
CFN1 6
CFN2 8
DFN0 4 ##### The DFNx prompts are the 3 external ring cycles #####
DFN1 6
DFN2 8
DNDH NO
TRCL 0
DFNR 0
CRT0 00 00 00 00
CRT1 00 00 00 00
CRT2 00 00 00 00
CRT3 00 00 00 00
DAY0
DAY1
DAY2
DAY3
HOLIDAY0
HOLIDAY1
HOLIDAY2
HOLIDAY3
In the example above,
CFN0 and DFN0 = RCO 0 which is set to 4 rings
CFN1 and DFN1 = RCO 1 which is set to 6 rings
CFN2 and DFN2 = RCO 2 which is set to 8 rings
I have attached a basic admin guide that might offer more help to you.
Firebird Scrambler
Nortel and Avaya Meridian 1 / Succession and BCM / Norstar Programmer in the UK
Very advance high level knowledge on Linux BCM with keycode support