BT Eqmt Terminating No. 24A / 25A

This unit comprises two halves each which houses an Alarm Unit 85A and a Line Terminating Unit 11A / 1 / 2. It's inputs are twisted pairs but the outputs are on two BNC connectors. I suspect that it is a 2MB/s device, but this is a calculated guess based on BNC and the internal coax connectors being used for 2MB/s circuits elsewhere ( but also for 34MB/s ), and the twisted pair line side connections could carry 2MB/s with SDSL, but the circuitry on the LTU card doesn't seem sufficiently advanced to be SDSL. It certainly isn't 34MB/s capable.

The unit is in a 3u approx size case but is not rack mountable, instead it has keyholes cut in the bottom to allow wall mounting. Ite cover is a brown smoked perspex which is incredibly static sensitive, it collects charge at the least rub.

Each pair of PCBs has it's own connector panel, the coax I/O is on the rear, but the twisted pair connections are made via an IDC panel which is accessible by removing the top.

This board seems to accept twisted pair I/O from the IDC connection board (lineside I think) and converts to a coax I/O for the subscriber side.

The lower half of the board seems to be a power supply section, the middle (presumably with sensitive components / processing filters etc) is covered with a soldered on screen so it is not possible to see that is under easily. The top half has an STC 5005 and a Texas Instruments chip, but I have been unable to find any data sheets. The crystal oscillator cans seem to provide clocking which is divisible easily, eg. 8.192 MHz (8192 → 4096 → 2048 → 1024 → 512 → 256 → 128 → 64 → 32 → 16 → 8 → 4 → 2 → 1Hz ).

This board has a loop in and loop out for each of the RX and TX coax connections from the LTU11 board to the rear panel BNC. There are a set of relays immediately behind the coax sockets, presumably for some sort of monitoring / fail over. There are two pcb mounted pin plugs which seem to connect the the IDC connection PCB on the top and the 9 pin D socket on the rear. Maybe these are dry contacts from the relays for activating an external alarm.

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