SIM 7600 modem - no voice AT functionality?!

I just received the first of a new batch of SIM 7600 4G shields.

I run the same code as I use successfully on SIM5320 chips, but have noticed the 7600 boards don’t do anything with the basic ATD, ATH commands, and don’t provide any incoming +CLIP or RING notifications.

Everything else seems ok - for initialisation, interrogation and SMS text messaging in & out.

Is there some extra magic setup, or a pin that has to be biased to enable the voice call signalling functionality ?

You need to tell what controller You intend to use. There's quite some difference between them.
What do You want to achieve in Your proj? SMS is working. Audio is a difficult task.
Reading Your Karma You're faar from a newbie.

Second round....

Thanks @RR, this modem is stacked directly off a custom MEGA 1284 board on Serial1
I’m a little surprised, because all the other functionality has been/is working and has been rock solid with the 5320s for a couple of years..., and I have debugging prints wrapped around the serial I/O - so I know the various (voice control) messages are being sent and responses/notifications not received back. No OK, ERROR etc.
Yet all the traffic for other commands are flying around exactly as they should.

I’m not actually using the ADC/DAC audio yet, that’s a planned feature, but I do acknowledge incoming RING and CLIP notifications, and initiate outgoing confirmation calls with ATD; and ATH (unanswered ’free’ calls !)

You're using devices way beyond my experience. You know a lot more than I do.

Getting the 7600 board working seams to be the issue.
Dig deaper in the documentation of the 7600 board and hopefully find an unsupported demand.

yep, thanks... that’s where I’ve started (and of course, wrote off to the shield manufacturer)... I have three pieces, one was a preproduction sample, and two more to work with until I finish the existing stock of (3G) 5320s... Thanks for the interest!

Issue found was AT+CATR didn’t default properly even though it returned ‘0’ (all)...
I explicitly set +CATR=1 (UART) and fixed the issue.
Now all voice commands & messages etc come through the UART port as expected.

Telling about a problem often makes people find the error.

Yeah, and expect the unexpected !
The doc declares the default correctly, the modem says it’s using the default, but the default doesn’t work.

I should test to see if I set the default, whether it works then !