I know that E&M is an analog trunk, that can be used to connect a PBX to a cisco device.
how many simultaneous call can we have on a E&M interface. do we have a kind of timeslot for each call as in T1 or E1 to differenciate the call. on some VIC card there are 2 E&M ports, how is made the connection : 1 port used between PBX and the cisco router, and the second between Cisco router and the PSTN.
E&M supports only one call per interface. Note that is most commonly used for connecting PBXs when PBX has already the ports available. Usage for connecting to PSTN is not common; check with you telco. The best option for connecting to telco is ISDN BRI or PRI.
Hope this helps, please rate post if it does!