Signalling TSLs depends on the vendor systems you are using. But in general 1 TRX takes 2 TSLs on a E1.
Motorola has combined signalling while Nokia has seperated TRX signalling and many more.
1:4 & 4:1 multiplexing/de takes place in transcoder.
16th TSLs for signalling is worldwide with PSTN networks and hence we use the same, as we do interconnect with PSTN.
Let me know if you require more information.