====== 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.

{{:rb:etu24-front-cover.jpg?250|}} {{:rb:etu24-front.jpg?250|}} {{:rb:etu24-rear.jpg?200|}} {{:rb:etu24-backplane.jpg?200|}}

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.


{{:rb:etu24-top.jpg?200|}}  {{:rb:etu24-connections2.jpg?200|}}  {{:rb:etu24-connections.jpg?200|}} 

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.
===== Line Terminating Unit 11A =====

{{:rb:ltu11a-1.jpg?200|}} {{:rb:ltu11a-3.jpg?200|}}  {{:rb:ltu11a-conn.jpg?400|}}

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 ).


===== Alarm Unit 85A =====

{{:rb:alarm85a-1.jpg?200|}} {{:rb:alarm85a-3.jpg?200|}}  {{:rb:alarm85a-conn.jpg?400|}}

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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