Bell System 801 Door Entry Handset - White

Product Information

I've just bought a replacement handset (Bell 801) for my door entry system. The existing phone that I'm replacing has 5 wires going to different parts of the handset but their destinations are marked A B C etc. It appears to be an old "Entryphone" handset

The wiring is a 'loop' system feeding the left & right side of the building. (2 cables, 1 for either side)I should also point out the old handsets have an internal 'buzzer' within them, which buzzes when a visitor presses the Intercom. x aforementioned circuit cables (looping either side of apartment building), each side using 4 coloured wires (1 wire for each apartment) & common red. One of the most popular kits on the market, the Bell 901 kit features a high quality intercom panel manufactured from 3 mm anodised aluminium with a brushed finish.

Can anyone help me to identify which wires go where (Z T 0 R 1) on the new handset? Please see the images which include the existing wiring (photo and diagram) at //www.diynot.com/network/DIYJunkie/albums/ The incoming wiring has red, blue (x2, for 2-way speech I presume), brown, grey (or at least it now looks grey after 20 or so years) and orange wires. The orange one goes to a single terminal (B) and then carries on to two other terminals (F and G). The others all go to single terminals. So...The 'loop' system serves as a single cable supplying 4 apartments (4 apartments on the left side), and the same on the other (4 apartments on the right side).