Owned an ISP. When we started we used USR Sportsters at 28.8k then flashed these up to support 33.6k. They were hooked up to Portmaster 2's.
As we went digital we used PM3's. I saw some 53k connections but it wasn't very common. Most common was 48k to 50k.
The PM2's were an amazing machine. We never had an issue with them in years of service. The PM3's were buggy until the later years. Eventually the firmware got good and they were very reliable. Rocky start though.
We had ours on retail wire shelving, there was plenty of room and airflow. We used the PM2's as reverse consoles after we went digital too. Thank god we rarely had to use them. But they sure were reliable. I had many PM2's with 1000+ day uptimes.
As we went digital we used PM3's. I saw some 53k connections but it wasn't very common. Most common was 48k to 50k.
The PM2's were an amazing machine. We never had an issue with them in years of service. The PM3's were buggy until the later years. Eventually the firmware got good and they were very reliable. Rocky start though.