Deployment viability assessment - freePBX + grandstream HT814 + Analog PBX

Greetings from India.
i am Noob to IP PBX.

I have a existing 2 trunks +8 extension analog PBX setup.
Now i want to move to a hybrid PBX using freePBX.

Have two pstn trunks (non fibre) from local ISP(BSNL), both presently connected to my analog PBX.

i want to transfer both the trunks using HT 814 or 812 ATA to my freePBX.
retain analog PBX with original two extensions and one extra extension.

FreePBX is running on virtual machine.
router and firewall is pfsense running on its dedicated bare metal hardware…no virtualisation

so my questions are…

  1. if i connect my both trunks to ATA and then connect the ATA to freePBX will i would be able to make outbound and inbound calls using softphone apps installed on cellphones?

  2. can i connect one extension of the analog PBX to ATA, so that analog extensions and IP extensions can have cummunication with each other and also outbound calling thru PSTN on IPPBX?

  3. is it necessary to have a seperate VLAN for the PBX system or can i use flat network with a single subnet?

In future the number of extensions are going to increase to around 50 and trunk lines may be to 4. my plan is to get rid of the analog PBX in a phased manner.

I am asking these questions so that i can decide if the setup is able to work reliably then only i would invest in the ATA and IP phones.

On the side note- i also have a FTTH connection with a voice line but the ISP has done setup at their end in a manner that the VOIP is on the private network of the ISP and only accessible on the PSTN port of the ONT modem. they are not willing/not able to provide with the public IPs of the SIP and proxy servers.

proposed deployment Layout attached

Welcome to the forum @puneet1984!

For interfacing with analog phone lines (POTS) your ATA must have FXO ports, one per line. To connect analog phones, the ATA must have FXS ports. The two ATAs you’ve identified don’t have any FXO ports.

  1. Yes. You can use an ATA with FXO ports to connect multiple analog lines to use as a trunk in freepbx.
  2. Yes. You can use an ATA with FXS ports to connect analog devices and use them as local extensions on the PBX.
  3. No, a VLAN is not required. The same IP networking rules apply to PBX and SIP devices as any other IP installation.

Note that interfacing with analog lines can be time consuming, and there is sometimes effort to get things like DTMF or Caller ID working.

Hello @lgaetz
Thanks a lot for the info.
Yes i did not check whether its FXO or FXS.
I would require FXO gateway for my requirement.

Can you suggest any cheap FXO device (4 ports) which i can use for home PBX setup.
Also any suggestions for a domestic calling VOIP plans for India?? searched google… no results … almost all provide calling plans for US/Canada.

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